For those who have ignition units needing at least 4.8 to 6 volts max to run, there is a step up unit available from Hobbycity which in conjunction with a single lipo delivers 5volts output to a max of 1.5amps. Looks interesting, I've ordered a few to try out. Good alternative to a 2cell lipo with a bec, that way you can charge the single lipo thru'the charge socket and dispense with having to balance the lipos. Under $5/- which is worth experimenting!

I'm running a single LiIon with my RCEXL on the FS-52 and it works fine. Step up is not needed.