ORIGINAL: airbusdrvr
If the trailing edge material is the proper thickness, taper, etc. but just to long, you can easily correct this. (1)Cut to the proper length. (2) Cut notches in the proper locations. (3) Glue the corrected TE in place. I can't see your plans while I write this, but the trailing edge is probably sheeted so all this will be covered by the balsa sheeting. Additionally, the balsa sheeting will make up for any loss of contact if one of the notches for a rib is to large. If concerned about the usused notches, just fill it with a small piece of balsa and CA in place.
I guess i lucked out in that the TEhas the notches in the correct lcoation, but i haven't checked for thickness and taper. All i would have to do is trim off the last 2" of the outboard end. Ijust wanted to be sure i wasn't missing something.
If the TE material is to thick, improper taper, etc. you still could use a profile view on the plan and sand it to shape and then use the steps above. If you have a good hobby shop close by, many sell pre-shaped pieces that might fit. With balsa wood, there is no such thing a mis-sized part. It is easy to make it larger or small.
Check out the before and after of the cowl below.
Alas, my nearest hobby shop is over an hour away, which is frustrating because i live in a fairly good sized metropolitan area with over a quarter of a million people, and there is not one single hobbyshop.
So I guess i'm going to call GP and talk with someone there to be certain. I may ask them to send me another set of TE's anyway.