you need to get a book on suspension geometry and do some reading and you'll understand what theese guys are trying to tell you. that thing has to have a lot of bump steer. your peice maybe strong but the tabs on the frame are not made for the extra stress put on them. go jump an 80' double and see how well it works out for ya.
I've run the amsoil dominator @ 50to1 with no failures for many years now in all my two stroke motors. buy it from an amsoil dealer in gallon jugs and it's cheap.
I don;t know about how much hp you gain, when I put them in my stock motor with +4 timing fmf fatty pipes and a k&n filter in the airbox with out a lid. there was definitly a noticable difference. they held up very well.