Thanks Andrew! That helps a lot! I think I want to make something maybe with velcro so we can leave it out of the bag and keep it from wobbling.Hey VTC, there are two tabs on the roof piece that slide in to two slots to hold the bottom, the top is held once you put it in the black leather case by two buckles that attach to two mounts on the back wall. You can see the mounts in the picture posted above vaguely as well as the straps on the pic of the leather case. I'm at work but can take pictures of it strapped later when I get home if that would help. If you put it in like shown in the picture without the case on it then it tends to wobble back and forth a bit. Unfortunately the case is kind of a pain to take on and off since it fits very snug but if you only drive the car when it is nice out and you aren't parking it anywhere out of your sight then it is nice to lock it down but if not then just make sure the passenger seat is scooted up a bit to prevent any long term rubbing on the top.
It does wobble a lot if it is just sitting there.