There Was A MB Seat Trainer at Fort Rucker, Alabama
I qualified on it in 1970 or thereabouts to fly right seat in the Army Test Board OV-1C and D. If I remember correctly, the rails went up about 30 feet and it was only a quarter charge. It still hurt my back a bit. The nasty part about the seat was that it was like sitting on a wooden church pew with no ability to shift position. You weren't supposed to have a cushion between you and the seat because if you did, on ejection with the real charge, your butt would essentially stay in place until the seat got to it. The seat would have accelerated quite a bit by the time it compressed an inch or so of cushion and arrived at the base of your spine. We were sitting on the thing for three or four hours on an inertial navigation test mission between strap in and get out. The other problem was the inertial reel on the shoulder harness was tightly wound. I had to periodically punch buttons on a test panel that was far enough away that I had to lunge forward, strain against the straps for a couple of minutes, and then be yanked back into an upright position. I'd have black and blue marks on my shoulders for a few days after one of those test hops.