I did all the spar work, front and rear, then built the ailerons and flaps. Reason being, I am building a new shop and don't want to jig the wings yet.
The ailerons and flaps are relatively easy - esp if you just finished the tail. The book says the flaps are the easiest control surface, but I thought the ailerons were the same or easier.
I can't think of any reason not to build them first...
Thomas
-8 wings