well, first make sure the seat belt tail for the center seat is not binding. then, push that bastard fully back at about a 45 degree angle - firmly. push but don't slam the nose of the seat down. Look under the seat - and the spring pins able to slide into the clip holes? If not, line them up and then push down hard.
you may want to check to see if you've bent the springs forward so they won't go the holes. it's likely a little difficult but not impossible to do that.
Bellevue WA
90 535iM - not much stock remains. 3.7 liters, ported head, cammed, 3.73 diffy, M5 brakes, MAFed, yadda yadda yadda
86 Porsche 951 - Track Toy