You can add all the aerodynamic devices known and reshape the wing using any tricks -(twist to add washout etc,) but here is the cold hard truth
most small ,scale aerobatic models simply can't be made light enough for easiy controlled , slow speed aerobatics
the wing loading simply is too high.
the very best you can do short of starting over -is to balance no more than 30% of MAC -then insure all surfaces respond and travel identically .
Seal hinge lines to prevent any difference in lift effectiveness from one side of the model to the other .
observe control at lower speeds and learn control inputs which keep you out of trouble.
adding inboard stall strips etc., is really futile.