I used a similar method to re-tramp my Hobie 18 with PVC/Polyester truck tarp.
If your tramp is totally gone, there's an easy method for that too.
Catamarans you get for cheap or free will need a new trampoline.
Trampolines get destroyed by UV from sitting out in the sun.
In case you're looking for a way to fix the kind of trampoline you bounce on, this same method would probably work fine for that.
I used Sunbrella UV-resistant cloth for the new tramp so it will last longer than the original one.
For comparison, here's how I re-tramped my Hobie 18 with PVC/Polyester truck tarp material.
Here's Damon, Audrey, and Star on the test voyage. The new trampoline works great!
The other photos below are top views of the boat before and after re-tramping.
Step 1: Take Pictures of your old Tramp
The frame of the catamaran is made from sections of aluminum mast extrusion. There's a slot in the edge of the extrusion. The sections of trampoline cloth have a piece of polypropylene rope sewed into the hem. That rope hem gets slid into the slot. That's how the cloth gets attached to the frame.
If your boat has no tramp at all and you're starting from scratch, don't worry.
These photos will give you an idea how the tramp used to be.
The grommets on the tramp are really massive. If you're making a tramp from scratch and don't want to mess with grommets, just sew a rope into all the edges of the cloth and lace around that.