I have switched some of my warbirds over to one (1) 5000MA Lipo this year and have been test flying this without any problems at all.
If there was any doubt with my baby's well being I would,'t be useing them.
I didn't want to have two different styles batteries (ni-cad/lipo) in the same plane for radio and engine power.
There is a bunch of guys around here with Smartflys that never have any problem doing the same thing.

http://www.tech-aero.net/ultra-ibec

Jim