After studying the plans a bit, I drew layout lines on the left seat floor panel where the three pieces of piano hing will be positioned so that the seat can be positioned for pilots of varying stature.

The plans seemed to indicate that the inboard end of the piano hinges should be 7/8" from the centerline of the screw holes on either side of the pushrod tunnel. However, when positioned thusly...

...the seat back doesn't rest against the F-705 bulkhead as it should.

Instead, one corner of the seat back hits the roll bar. Hrm...I'm going to have to do some research on this.

Okay, after reading some threads on VAF and studying the plans more, I realized that the section of hinge I had attached to the seat back was not made per the plans. See how at the inboard end of the hinge (left end in this picture), there is a 1/2" length of flange without a hinge eye? That's supposed to be cut off. Doing that eliminates 1/2" of the 11/16" of interference. However, I'm going to have to move the seat back inboard by 3/16" regardless.

Here's why: When I built the roll bar, I planned ahead for the canopy attachment via Sikaflex sealant. Sikaflex requires a minimum sealant thickness of 1/8", so I reduced the width of the roll bar by 1/8" on each side (also on top). Moving the seat back inboard by 1/8" would compensate for that, but this design is very tight. I decided that another 1/16" would be prudent to allow a bit of clearance with the roll bar.