Thanks for the replies guys!
For the record... my garage is unfinished, so I can actually see all the studs, outer wall, and rafters.
I have tried hanging straight from the rafters because they are much bigger... and couldn't get a good hang with my hennessey. I think if I could adjust the ridgeline it would work better, but, alas... to no avail.
I also tried hanging from the 2x4s that were already installed in the sides of the garage, but they're too low, I'll have to figure out the perfect height and put a couple more up, or make a stand. The problem with making a stand is that I really only want to set it up so I can test my shelter system outside, and if too cold/wet/whatever, I can still bail to the house.