Just use regular nuts and bolts and back up plate on the other side of the trampoline. For nuts and bolts the smaller size the better. I think that I have used size 8-32. make back up plate the same shape as your footprint of compass and drill holes in the same spots where your compass has.

If your trampoline is made out of mash then you should have no problem to push through small bolt.

Use stainless steel bolts and self lucking nuts.

Kris