I did the strap thing a few times. I installed 3 grommets on each side piece of the tramp where the straps used to be sewn on. The first time, I used a dog leash size nylon strap. I thought it was a little small, so I replaced it with a life jacket one. You will have to get special grommets if you want to use something big like a seat belt piece.

I tied a knot in one end of the strap and passed it up through the grommet at the front of the boat. I then ran it to the grommet in the middle of the boat and down trough it. I tied another knot in it under the boat and passed it back up through the grommet. Then, I ran it down through the rear grommet and tied one more knot under the boat. Pretty easy!

I suppose that you could use the seatbelt piece in the same fashion. You could probably tie it in a knot under the tramp and run it through once, but it proably won't go through the same grommet twice. You could use a larger diameter piece of rope by tying a knot in the end (under the tramp) running it up through the grommet, around the seatbelt strap and back down through the grommet. Finish it off by tying another knot in it. That should work to hold the strap down.

I bought a grommet kit at Home depot. It came with a bunch of grommets, a punch and the setter. Granted, that was a little bit of an investment, but I have used it MANY times and it was a lot cheaper than taking the tramp somewhere to get it fixed.