I made several tests to create a powerful bounce poly.
My original idea was to put several polys in chain so the player would be pushed forward. That didn't work, but I discovered some poly distribution that have a greater power than the regular bouncy polys. It uses 2 bouncy polys:
(note that is better if the "normal" poly that give access to it is slightly downwards)
I attached a map using it. I added a regular bouncy poly so you can compare.