Andrew R Stewart 

Is there a problem with the functionality of this frame? Does it track straight? Does the rear wheel fit well? If the answers are no, yes and yes then I suggest don't do anything but ride the bike. If these are the answers then there's no functional issues and only cosmetic ones.

Al does not do well with multiple manipulations. Focusing the straightening to the same spot and with the exact support needed to end up with no remaining ripple or slight dog legging will be near impossible without very involved forms and control. Having done many steel (and a very few Al) stay straightening I can speak form experience that even with the bike industry provided tools this type of realignment is not straightforward (pun much intended). So consider any repair to be a make better but not great at best and mushrooming into really bad results at worst.

If the wheel sits slightly crooked (and I make no assumption that it did when new...) then a few file strokes on the LH drop out, well focused, will cure that. If this is "Greek" to a reader I suggest that reader not be the one to do so. The brake might be slightly off center but that's what spacers on the pad mounts, eye bolts and centering spring tensions are made to correct.

Given the nick name of this brand, crack'n'fail, I would suggest to deal with the wheel alignment in other ways then bending the stay. Andy