Where can a civilian obtain centrifuge training/testing?
This is a tough one. I don't know of any civilian facilities (but it does not mean they don't exist). This is a bit of a shot in the dark but in my opinion you may want to contact NASA about the Ames Research Center 20-G centrifuge. If for no other reason than this is the only non military one that seems to exist. For what its worth high speed centrifuges are not that simple despite just being something that spins in a circle. The speeds that the unit spin at are extremely high to say the least, to do this with out ripping the whole thing apart requires careful balancing and construction so they are not exactly something you can build at home. Here is at least one company that is building them and installing them elsewhere in the world. They list a bunch of installs for other militaries that might be more open to a civilian coming in but who knows.