My advice is a little more mild of an aircraft than the Something Extra. Go with a Four-Star 40.

Same easy to build high quality lazer cutting. (a few more parts to deal with)

The performance will be a noticeable improvement from the high wing trainer... but it won't be as touchy as the Somethin Extra would be.

The one thing you need to do to get best success with the Four-Star... put on a longer lower pitch prop. 10X6 on a .40... it won't slow down for landing with the engine running. 11X4 and it will make the smoothest landings yuo could want... come to a full stop and then you can hit the throttle and fly some more. (practice landings and take-offs. its good for you, and your airplanes.)

Don't try to advance too fast... you just end up breaking balsa.