OK, I didn't read all of this but wingloading and speed are still enemys. Lots of speed lets you fly with a higher loading but higher loadings slow you down. The need to generate more lift results in more drag. This really shows up when you load up the wing in a turn.

Very light and symetrical or close to symetrical airfoils are the way to go. And SWR's? The flat airfoil works best with minimal angles of attack to ensure low drag. Again light is right on these.

As for landing and taking off the small size of wheels and small wheelbase kills the small models. But if you have a paved runway available then you can make small models with small wheels and they'll do fine. Otherwise you darn near need a golf green to land and take off.