Well, old experiments are unaccepted because they are old, experiments you can perform yourself are either considered useless as a detailed report hasn't been published based on them, or useless as they could be valid from a FE point of view, experiments that rely on the planet being round are useless as they are not designed for the sole reason of checking the shape of the planet, experiments that prove the shape of the earth as a byproduct of their main function are useless for the same reason, the common knowledge of the shape of the planet is useless as it isn't based off of an easy to perform experiment, maps developed by cartographers and such are useless as they aren't produced for the purpose of proving the shape of the Earth, Measurements and such used by telecommunication companies are useless for the same reason.
Devices put into orbit are useless as they don't exist for the express purpose of proving the shape of the Earth, or because NASA or some group that at some point may have been related to the government was involved in them at some point, NASA and government contractor information is considered useless as there's a chance that it may have been tainted by the conspiracy, Observation data of other objects that are in space is useless as the rules that apply for every known stellar object may not necessarily apply to us, physics theories that suggest the planet is round are useless as there's no way of proving that a theory is 100% correct, and direct photos of the planet showing it as a globe are useless as images are apparently not considered valid research.
Well, I think I'm out of ideas for now. Perhaps if someone found a 130 year old book that explained why the Earth is a globe, it might be considered valid...