Use the cell count as recommended by the manufacturer. Reducing the cell count will result in less power possibly even makng the airplane unable to fly. Address the heat problem as outlined by Jester above. Twenty minute flights are far to long and will kill your batterys in short order.

Using a different color on the right and left wings is a big mistake that will result in loss of orientation every time.. Using contrasting colors on topside/underside is a good plan however that I would recommend. Many different fancy colors and designs will fade to grey at a distance much closer than simple colors witout a lot of scroll work.

John