For the rear part of the new main wing ribs, I keep it pretty much the same as the old profile, adjusting the little triangle at TE. At first, I got the new wing chord 18 mm. short. Now, maybe, it's 1-2 mm longer.
Since my airplane was completed and flown before wing re-build, I keep the flaperon hinge line in its original position. SInce you are building from plans only and I haven't seen how far you are in building the wings, I will suggest this: Build the wings, Install the wings, Determine the hinge position.
Draw Wing Rear Rib (7V1-2), using paper template, on a piece of plywood. Draw Flaperon Bracket (7V4-6) and Flaperon Arm (7V4-7), also using paper templates on the same plywood just as they are assembled correctly to 7V1-2. Mark the pivot hole for flaperon hinge. Now, you can use the drawing on this plywood piece as a jig to assemble the NEW flaperon arm to each wing rear rib and have the holes for hinge pin all in-line. As a matter of fact, I got the shape of my new flaperon arm from this finished drawing on plywood.
After you install the wings on the fuselage, complete with wing struts, you can bore-sight through hinge holes on flaperon arms of each wing and mark the spot on the fuselage for the Root Hinge Pin (7A2-4). In doing this, some use laser pointer, some use small steel tube, while many simply use Eyeball MK-1 and walking back and forth (working alone) to mark the exact position.
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