That is my only concern with the aluminum, but I don't think it actually points at the fenders but I will let you know once I have it installed. The stainless does not come with a spark arrester which is another $20 to buy..the aluminum does. Plus a got a GREAT deal as this guy negotiated with me the other guy didn't.
I don't think the aluminum tip is 2", it is actually only 1 5/8". If you are looking for more performance the 2" ss is the way to go(not to mention my friend sells the 2" ss tip on e-bay so I'm a little bias).
I made mine out of 2" aluminum electrical conduit bent about 70 deg. and welded to an aluminum flange that I turned at home. I bologna sliced the end to exit straight out the rear and polished the whole thing to a nice satin finish.Total cost $5.00 to have a friend weld it up.