RE: slinger/mini slinger
I wouldn't go with lipo because it will burn out a brushed 400/480 motor. Also i don't see how the CG will balance out. I use a 8 cell 1150 mah NIMH and i still have to add 1/2 ounce of weight towards the front.
I usually get some help or launch over a small hill. I grab it in the back and launch it without power, then go full power after i let go.
When i first launched, it went fast into the ground since the control didn't have enough up to it. It seems they should be just above level with the ground in order to fly level. In in doubt, try adding more than you need.