Keep in mind that most Extra 300 style of models are intended to do a lot of snapping maneuvers so the elevator throws suggested by the makers are intended to make the wing stall easily. It's up to you as the pilot to moderate your elevator input for those times where you want a tight loop without the stall and snap. If you were to set the elevator throw to a lower angle so that you didn't stall the wing so easily then you would still be posting here but instead of complaining about stalls and snapping out of turns you'd be complaining that your Extra wouldn't snap roll cleanly and do those nasty 3.7 turn Lomcevaks! ! ! ! It comes down to the old story about "be careful what you wish for" and "you can't have your cake and eat it too" and other such platitudes

Seriously though, if you want the model to fly the snapping maneuvers then you need to just learn to walk the tightrope for the times you want it to loop tightly. All the options for adding turbulators or flaperons were intended to reduce the tendency to snap roll and adding them may not be what you finally want on a model that is intended to snap roll cleanly on demand.

The sort of tape turbulators I was trying to describe are not a fold line in the tape but instead to just cut thin strips of the tape and apply multiple layers to build up the thickness to what you find works out. Keep the tape down to 1/8 or slightly less wide. In the case of trying saw tooth strips you need the wider tape but it's cut in a pattern along the leading edge of the tape in a oversize pinking shear scissors like pattern. Again you want to lay up three to four layers of this tape before cutting the sawtooth pattern.

Although if you can cleanly tape on a bit of wire to the wing so that it is about 1/32 high and get the tape to cleaning rise up over and back to the wing with sharp corners that should work as well.