I use a similar set-up on my Savex L-39/ Wren 44. I have a Jeti Li-Ion 5200mAh pack that runs the radio, engine, retracts and brakes. I can get at least 10 flights before needing to recharge. I use a BEC for the radio though as I have standard voltage servos. Going HV would eliminate that need.
A perfect solution for a small model.
Paul