Mr Clock Tower,
I deliberately did the maths for a 6 metre length of glass to address your concerns about tolerances. Please check back through the post.
A 6m piece of glass will be curved by 0.47mm. As the article by British Glass states, they make glass down to 0.4mm.
Therefore no amount of shaving will make it flat as you will cut away all the surface (0.4 mm of it) if you cut 0.47mm into it to get it flat. And as stated if something curves 117.5% of its total thickness, it certainly cannot be said to be "perfectly flat, flaw-free glass".
As for one piece of evidence, I have constructed a deliciously thought-provoking second example to help prove the earth is flat, that I hoped to post this evening. However some of the data which I know to be true, I have only found numbers for on wikipedia, yahoo answers and forums. Being as I now have a flavour of RE scepticism, I will postpone my challenge another day or two, until a more trustworthy source can verify for you the starting data. I wouldn't want to leave you in any doubt.
Mr Jackel, I have reiterated several times already, that the bottom of a liquid has no bearing on the shape of the top of it. No amount of levelling the tank is going to change what happens to the surface. On a round earth the fluid will emulate the shape of the earth. - i.e curved. The fact that you can't grasp this fundamental concept, puts your IQ in question far more than my own.
Mr Kira. Perhaps you would prove eclipses to me first from a round earth perspective. I would like you to concentrate specifically on why the moon is exactly the right distance from the sun and earth, to exactly cover the sun and not be too big or too small. I would also like you to explain why it is the moon always faces the earth so we always see the same side of it, and that it spins at exactly the same rate as its orbit time (roughly 28 days), but yet that the earth doesn't always face the same way for the moon. Coincidence will obviously not suffice as an answer for either issue.
I'm off now to see if I can find some authentic sites, with which to submit my next puzzle.
Have a good evening all.