I had this.
When I built my first aileron on my 6, very similar aileron to the 7, this happened to me because it was sitting on the bench and I assumed it would stay straight as I tucked it in and drilled the holes. WRONG?
When I took it out to de-burr the spar went back to straight but the holes were in a curve.
Silly me, I should have known better than to make any assumptions.
When the new spar came in I REMEMBERED to use my edge distance marking tool that I made to accurately mark the cent line of the spar.
It is a piece of wood with a super fine sharpie and an adjustable stop.
I marked two lines about 1/16" apart in different colors.
You may not actually be drilling in the exact center of the spar, but with the marks you will get a very good idea if its straight as you go
My second attempt came out straight and beautiful.
I am glad I messed up early in the game as it helped me be more patient and careful with the resat of my project as I still go along.
![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)