I bolted mine with small aluminum angle that went between the panel fixing points and the side seams of the opening. I also saw a nice job on another car where they bent the side seams over than pinched them between the panel and the metal bracket that surounds the panel.

If your pinched for money, make sure you get out what you can. If your sunroof is working properly it is worth decent money on ebay. Mine worked fine and I took a short video of it opening and closing and got $90 for it on ebay without the panel. Some of the ones on ebay with rust-free panels were going for $200.