That is a big gap. On a trainer that will not cause too much trouble but as you move onto faster more aerobatic planes it can cause flutter by air slipping between the gap. Some people seal the gap with clear monocoat. When I assemble control surfaces with CA type hinges, I gap them by putting a "T-pin" through the hinge and pushing the control surface to the stabalizer/wing until the gap is the size of the T-pin.

Go [link=http://www.hangar-9.com/ProdInfo/Files/HAN4250_Spitfire_60_Manual.pdf]HERE[/link] and scroll to page 8 of the manual to see what I am talking about. This is the manual for the Hangar 9 Spitfire but the technique still applies.