rectangle bounces the best and is the most safe. Avoid round ones. Octogon and all the other shapes aren't as good as rectangle becxause on a different trampoline (square for example) the way the tramp is made, if you bouce outside of centre it will double bounce you the opposite way. therefore, shooting you off. On a rectangle one, the tramp is designed so the spring pattern is criss-crossed evenly and you dont go all over the place no matter where you jump. And because you are closer to the edge, closer to the spring= more bounce. I have a octogon one and i crossed the springs and it doesnt come close to my friends rectangle one. he doesnt even have the springs crossed.
Rectangle is the way to go