Today I completed the front seat assembly. First I fabricated a hinge pin (10-3/4" long total, bent 3/4" from one end to provide an easy-to-use "handle"), then I installed the front floorboard in the fuselage. Next, I mounted the seat to the floor and clamped the seat's top angle in place with the required 1/8" clearance from the WD-808 roll bar. Then I removed the seat and drilled the angle to the seat.
After this, I un-clecoed everything, deburred all 6 parts (seat back, two side angles, top and bottom angles, and the hinge), and Scotch-brited/cleaned/primed them all.
Finally, I riveted the seat rails to the rear seat back, primed the attach hinges, and clecoed the hinges to the seat. I'll rivet the hinges next time, and also begin fitting the fiberglass part.