I bought some new ammo (foam practice golf balls). These don't have dimples and are a little stiffer. They now fire half-way across our yard with no burst diaphragm...perfect for the kiddos. Here's a video of a launch with a Duck Tape diaphragm. I don't know if you'll be a able to see it but the ball flew straight into the tree at the far end of our yard. Without a tree impact it goes part way into the neighbor's yard.
I still haven't decided on a mount.