Dear Astronomer, I'm very sorry you misunderstood what I was trying to say, but it really is my fault, because I misunderstood what you proposed. Let me try to make amends. 
Any horizontally-stretched wire, no matter how tight the tension, will always have a deflection due to the force of gravity movement across geodesics.
First of all, FE folks say that the earth is accelerating upward at 9.8 m/s/s, because gravity doesn't exist. In this magic elevator model, everyone will experience gravitation, which people like you and me call just plain gravity. But the result is the same.
Draw a free-body diagram for a 1-foot section of the wire, in the middle, and you'll see there must be deflection.
You seem to be one of the more educated people here, so I assumed you knew what a free-body diagram was. What I meant is that a 1-foot section of wire will have tension pulling left and right (represented by force arrows pointing 180o and 0o), but will also be subject to gravitation, even in the FE model, represented by a force arrow pointing down (270o).
In a free-body diagram the lengths of all arrows represent the magnitude of the forces involved. And in a static (not dynamic) system, these forces must all sum to a zero vector.
If your wire were extremely lightweight, the down arrow will be extremely small. But it will be there. This means, since there are only three forces acting on that small length of wire (two tensions plus one gravitation), that the tensions must have a vertical component as well, even if it is very tiny, meaning they can't be at 180o and 0o. In plain English? The wire cannot be perfectly horizontal.
Why not suspend the wire along side a skyscraper? That will give you plenty of distance.
Ok, here's where I did the "epic fail" thing. Halfway through your problem I completely forgot why you were tensioning the wire, so I simply proposed an easy method for tensioning a wire with no deflection, vertically along side a skyscraper. No wonder you didn't know what I was talking about!
I had just been reading about some Harvard professors who conducted an experiment with redshifting electromagnetic waves using the Earth's gravitation, and they did it in an elevator shaft, with success. So in my mind I was sort of thinking about that.
First off, you have no need to apologize, and let me apologize to you and robbyj. I had a lack of sleep and a surplus of alcohol the night before last, was looking for a fight, and really took the piss... I know that's not a real excuse, but I should by all rights have kept myself away from any and all cell phones-internets. At least I didn't do as bad here as I did at sites unmentioned.
Second, thanks for the complements, but keep in mind that math is definitely not my strong suit. I'm an art's and philosophy major, know just enough math to get me by, and keep all the algorithms I use in max and other endeavors bookmarked for fingertip reference. That's why you won't see me in the math threads here. I can't swim in those waters, and they're way over my head.
On the wire experiment issue I'm totally getting what you're saying now. I was aware that there would be some arcing, and I was willing to accept a tolerable degree of deviation, but I'm starting to see that the arcing on a wire that length would give deviation that I wouldn't find acceptable, let alone the rest of the posters here. I'm trying to think of some ways to scale it down so that it's more workable, and yet could still give verifiable results.
Please keep up the good work carrying the RET torch. (Love the 3D Studio Max!) 
You keep fighting the good fight too. The "see the sticky" response I keep seeing you getting isn't very good debating in my opinion. I'm sure that for every 30 page thread they've told you to look at where some poster made a hypothesis 15 pages in that kind of backs up FET, but is unverified by any kind of experimentation, you have knowledge of dozens of experiments, well documented, and reproduced by peers that controvert it. It must be frustrating as hell to be told again and again that the works of the greatest minds on the planet, and the greatest minds of the past are meaningless in debate and reality because they are all part of some grand "conspiracy" that they can't prove by any means but hold true nonetheless, and hold you to by proxy. I know it frustrates the hell out of me.
The part that makes it personal to me and brings my ire up, is the assertion that all world leaders and governments are just keeping up the charade of turmoil to cover up this "conspiracy". Anyone else with family in the service probably feels the same way. Can any FE'es honestly say they think Iraq's a charade, Darfur's a charade, or that the Georgia conflict, and Russia back on the defensive is just a charade?
Yes, please keep making the diagrams. I don't have the ability, and love having them as reference material.
Thanks. I love making stuff. If you, or anyone else, FE or RE, have an idea for me I can flesh out, let me know. I'll put it on my to-do list.
Stringing up a wire between two trees sounds like a crazy idea..
Why not do an easier version? (still very hard to do though, for a hobby scientist)
Set up two mirrors, exactly 90 degrees to a FLAT horizontal plane. Bounce a laser between the mirrors. Have photo-sensors count the bounces to get the total distance. See if the laser wanders upwards/downwards, and use that to rate to the distance. You get the idea..
I personally like the idea, but I don't have that kind of fluid cash to be throwing away on a hobby exercise, and it's been done anyways many times for multiple non-related experiments with no noticeable vertical wandering. I'm sure FE proponents would say that striking the vertical plane re-aligned it straight again, it's all a big conspiracy, or something like that. That's why I picked the simplest kind of experiment for my proposal. Emitter -> target... All I'm concerned with is getting pre-experiment deviation to an acceptable level.
Ok, I was thinking about the vertical wire idea, and I have come up with my version of the experiment, it uses 2 lasers 1 is perfectly vertical, the other is at an angle, as the lift decends, the dots will converge linearly if the light is straight, and non linearly if it is curved.
On the diagram, the left hand red line represents a red laser of straight light, and the green is if light is curved.
The only disadvantage is that the curve is supposedly less at incline so would need more accurate equipment.
Also it doesn't need to be a lift shaft, a window cleaners basket would work the same, as would a board lowered down a stairwell.
Another way of doing it would be like in the second diagram, 3 equally spaced vertical lasers shone upwards, and 2 shone downwards. If light is straight, they cross halfway up, if it is not, they cross less than halfway up.
It would probably work in the RET world, but FET proponents say only horizontal light curves, and even if you proved something, it would be meaningless to this discussion. That's why I'm proposing a horizontal test. If you're interested in that though, and want to have a real world discussion, try talking to cbreiling... He seems to have a good grasp on things similar to what you're proposing. He could probably tell you if it would work or not.