I am operating a gasoline powered F3A model (SAP180 engine), and use and highly reccommend TECH AERO regulator and TECH AERO IBEC. Both the regulator and IBEC have field selectable voltage outputs.....of course the regulator feeds the RX and the IBEC feeds the CDI unit. The Ignition Battery Eliminator (IBEC) also optically isolates the signal for maximum possible rejection of spurious RFI returning to the RX. It is remotely activated from the TX.

Both components require a single 2S lipo or Liion source. If you use a LiFePO4 battery with its nom volatge at 6.6 or so, then you don't need the regulator but should still use the IBEC.

About as bullet proof as you can get with this set-up plus it is extremely lightweight. I have both the regulator and IBEC in my plane with a 1780mah 2S2P lipo and the whole thing weighs about 5 ozs. which is less than 1 1650 NiMH 5 cell pack.