I've had the Hitec Feather RX glitch bad on me when flying with other TXs... not sure if your HFS-04 will reject adjacent channels any better. Everyone at my field flies dual conversion RXs only in nitros.

I'd spend the $$$ and get an OS engine, but that's all I fly... they run great and are easy to tune, so I don't care to mess with any other brand. The OS .50 SX is what I put in my Avistar... the .46 AX is a little cheaper, and is a good engine as well. The .50 is ringed, the .46 is not, though...

Get an electric starter... safer and easier...

Your 2/3A batt pack should be fine... get a Hobbico VoltWatch battery monitor for it to be sure you don't try to fly with a low battery...