Recent versions of the Xicoy ECUs are rated for 4-10Volts on the 3 wire receiver input line. I can't confirm the current V10 ECU used with the 100G is the same, but it is likely.
I have at least one fellow jet flyer using a K170 and a HV receiver dual battery system (Lipo). I do not believe it is regulated at all. I'll check.

Barry should be able to confirm you are good with 7.4 from the receiver to the ECU.