LennyC welded a couple flat brackets to his frame tubes in the very front, cutting small slots into the fiberglass. His tow bar attaches with a couple hitch pins.
I don't think he ever bottoms out, so they aren't too low.
I use a custom towbar. The speedster bar most probably won't work, as there are frame tubes welded to the beam on Spyders that make the space 3 to 4 inches narrower than a stock beam/towbar.
Not a big deal to modify or make a new one though.