I’ve heard that most if not all builders have a problem with the seat backs interfering with the roll bar. I took a measurement off the plans, and the rollbar is 3.5″ from the outer skin to the horizontal bolt on the inboard edge.
I measured 3.5″ in from the skin along the front edge of the seat back support and made a mark.
With the outboard edges of the seat backs positioned flush with the end of the seat pan hinges…
…the top of the seat back extends past the mark by just over 1/4″
If I move the seats over by one eyelet…
…then the top of the seat backs are inside the roll bar by a little less than 1/4″. Building the seat backs according to plans, but swapping the left and right seats will result in this inset.
I cut the lower hinge for the left seat and match drilled it and the lower angle to the seat back.
Here’s a closeup of the lower end of the angle showing the notch that is cut to make room for the hinge.
With the left seat back installed on the right side of the plane, I was surprised to see that the seat back was perfectly in line with the cutout for the controls. If the seats were installed according to plans, not only would they interfere with the roll bar, the stick would not be centered between your legs.
