F-715, DWG 22

Clarification please.
The manual describes fitting the F-715 ribs. Draw a center line on the bottom flange. Align to the skin holes and match drill. No problem. I had to flute them to get the center line aligned.

Then it says to position the top flange so the web is .032" outside the outer edge of the seat skin.
I understand the instruction. I don't understand why. The only explanation is clearance to get the seat skin removed/installed. I don't see anything outside the rib that might need .032" clearance.

Also, does this apply to the forward floor skin as well or just the seat skin?

I think it serves two purposes: 1) facilitates installing/removing the seat floors; 2) to keep the seat floors from contacting the side skins and potentially wearing on them.