Advancing your flying skills would be the goal... and one of the best choises for that is the Sig Four-Star 40.

Its not a huge leap up from the trainer you are used to. The change to low wing symetrical airfoil and taildragger will present some minor challenges right off. But the 4*40 is known to be one of the tamer taildragers.

Its aerobatic ability with a .40 to .46 is outstanding... so you don't need a new engine. (read my post regarding prop choices... use the 12X4 it makes a WORLD of difference.) Its still stable enough to not destroy itself when you make a slight error too.

A definite step up in capability that can be flown by anyone that has soloed with the traditinal trainer.

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Very similar, but heavier... the Golberg Tiger II. Another good choice... but not as good at consecutive inside-outside vertical 8's unless you get a Irvine .53 or equivilent power.