A 6s setup for a 30" hull is a lot of power. You could easily get away with running 5s or 4s. At 36" a 6s setup will be sufficient.

The leopard should handle 6s at 1550kv. You can start around 37mm for prop and work your way up if you don't feel comfortable. As long as you follow the guide for your [link=http://www.radiocontrolinfo.com/ElectricBuild/pre-testing.html]First Run[/link], you should be fine.

Leopard offers a 1450kv version which will allow you to spin a larger prop.

Ryan