A go at a Foamie

It may be the camera angle, but it appears that the servo is mounted too high, so there is a bend in the cf rod!
Cut away that lump of foam and the balsa? stick, then make a notch n the fuz side, so the servo arm can be dead in line with the outer tube.

For a simple, slow-flyng lightweight, Blenderm adhesive tape is perfect.
It is almost clear, stretchy, and sticks almost as well as Gorilla tape, without the dense black and heavy backer.
Blenderm is a 3M product, and is used in hospitals for temporary patches such as a cotton wool pad over a hypodermic stab-hole. You may have to resort to e-bay to get it, if your local model shop or chemist doesn't sell it. It can be obtained from HobbyKing as well, when they have a stock in, but it goes fast!

As Q put, - but think of the long (span) wing as a lever and a fulcrum, the fulcrum (pivot point) being the fuselage. a longer lever (the wing span) requires less effort to move the load.
Where it gets complicated is when you start to think about the drag - for a given length of lever, a larger (in chord) control surface of the same length (span) deflecting over a smaller amount creates less drag than a smaller chord surface at the same distance, which needs a greater deflection to achieve the same roll rate. And you can reach the point where the surface 'stalls' and has even less effect - or merely becomes an air-brake.
Compare the control surface sizes of an indoor 3D model against those of an outdoor faster model!
Then - you have to consider the static mass of a wing - a heavier (longer span) wing takes longer to start and stop reacting to the aileron deflection than a lighter (shorter span) wing, which is why a small model always seems 'twitchy' when compared against a larger one, and why a glider has (generally) a longer fuselage from the c of g to the tailplane than an aerobat.
Aerodynamics is a complex and huge field! And then, because you cannot scale down the air molecules - model aero's are even more complex! The more you think about it, you realise the less you know!
There is a book titled "Model Aircraft Aerodynamics" written by Martin Simons, - if you really want to confuse yourself! It might still be in print.

www.amazon.co.uk/Model-Aircraft-Aerodyna...ripbooks%2C53&sr=1-1

I wouldn't use any Cyano products on foam without testing on a piece first, Simon uses Uhu Por on a lot of his foam airplanes. Personally I don't like it, I tried it on PLA filament and it fell apart when the model fell to the floor. Almost any zero solvent glue will work, I personally like Pattex Extreme Repair.
 
It's certainly available in Holland, my Nephew got me some. Do not buy the 100gm container, it time expires very quickly, something to do with the container not sealing properly. Ask me how I know.