Improving the hinges in an existing aircraft is actually quite straightforward. Assuming your current hinges aren't too tight (i.e. no servo stalling when actuated), you can overlay strips of Monokote over the hinge line to seal the gap. This reduces access to your hinges for routine inspection (you do inspect your plane as a preflight, don't you?), so make sure you trust your hinges implicitly before doing so, or leave uncovered accessways to the hinges so you can assess their airworthiness.