Pat -- what's your top speed? Total amp draw? Total thrust?
On a 3s LiPo, I'm looking at 46.7 mph, 44.4 ounces of total thrust, at a total amp draw of 13.5 amps.
The same power system on a 4s LiPo, I'm looking at 59.9 mph, 73.4 ounces of total thrust, at a total amp draw of 21.3 amps.
My goal is to keep the amp draw low, so I'm wanting to stick with the 3s LiPo setup... If your numbers are similar to mine, I will consider switching to the outrunners. However, I currently have outrunners in my Flying Styro P-38, and I'm not happy with the 24.8 amps it pulls at WOT.