From what I know, Cubs have about 1 to 2 degree dihedra! Does not seem much, and is almost unnoticeable. BUT it increases stability. The best thing to do is to take reference from your plan.
Back in the 70's, my father did build the Sig cub 1/6, full wingspan. Very nice plane, well build, covered with silk. He did have a Enya .25 or something like that ( we used cc) that thing never went of the ground...was waving left to right, never made it. Back to te shop, installed an OS .35
problems to track straight...decided to hand launch it...crashed after 50 yards! Must have had a problem with cg? we will never know. Friend of ours had one too, with a .40 engine, and it flew perfectly! Go figure it!
So, check that dihedra, and make sure you have an engine that can get you of trouble too.
How do you plan to make the fake cylinders heads for the engine cowl?
Keep us informed
Al