We have had a tramp for 6 years with no accidents. We got a new one last year, gave the old one away. New one is a springfree one.
We have rules too, and they work because we are always there to enforce them.
1. Only one at a time
2. Net to be closed
3. No hanging on the outside of the nets
4. No going under tramp
5. Only allowed to do skills that you have done alone in the gym with a coach present ( only applies to my kids. When we have friends over all kids have to stick to bouncing, never flipping).
6. Only allowed on tramp when I am watching.
7. No coaching friends on the tramp.
8. no bouncing on the tramp when it or you are wet.
Tramps are dangerous, but many things are, we enforce the rules 100% of the time, no negotiations. The kids have a blast on it even with all the rules. It is like a pool, a good set of rules and a fence will keep your child safe if you stick to them. If you are a jellyfish parent and cannot follow through with the rules, DON'T BUY A TRAMPOLINE OR POOL.