Replying to Inground Trampoline?

I'm getting a new trampoline soon. It is the sky walker 9x15 rectangle one, I've heard it's got a pretty good bounce. I am going to be putting it in the ground and was wondering if anyone has any experience with inground trampolines. I was wondering if it will effect the bounce at all and if there are some tips on how to ventilate it properly. I currently have a small 8 foot round trampoline in the ground and it has a very bad bounce and feels very stiff and hurts my back if I use it too long. Any tips on how to make the inground trampoline have a better bounce?