I suspect the guys who have given up are not watching the forum, so you're going to get responses from a bunch of hard headed types who have stuck it out through all sorts of challenges.

I know I have had some models that did not fly up to my expectations.

You don't say how much flying experience you have, so forgive me if it is more than my next comment assumes. Get somebody else, perhaps an experienced pattern flyer if there is one around, and have him check the model, fly it and trim it. A second set of eyes may pick up on something you missed.

Chuck