I have been training a new pilot at my field on a NEXTSTAR that came with the airbrakes. These allowed the plane to land much more stable, but hindered normal level flight. I flew it this way the first time with the new student, but decided since he wouldn't be landing soon, I would take them off so that the plane would fly better without them while he was training how to fly level and make turns. The airbrakes (flaps) really slowed the plane down and made it much more stable than not using the airbrake. Another guy that I have helped actually has three servos in the wing and has cut the ailerons to make two flaps and two ailerons. This thing floats forever at a crawl.

I think if you set up flaperons it would help or put three servos in also the way the Nextstar can be done would help out with the landings. However, the setup would not be worth the work on the avistar unless you plan on flying it for a while, but chances are you will move on to another type of plane. On windy days though, I don't use flaps on my planes.