ORIGINAL: aerobob
And I'm the "friend" (thank you, Dick.... ) and I've never mounted a gas engine servo ANYWHERE but **on** the engine box. Until this season, ran only JR PCM on 72Mhz, and didn't have problems. I don't deny that the manufacturer makes recommendations that they believe are "guaranteed Safe", and I think that's a good thing.
I am not the ONLY person that has installed servos on the engine boxes.... in fact, if you polled for that question, I think you'd be surprised at the responses.
And yes, so far, the direct-connected A123 battery is working on my RC-EXL ignitions; I cannot state whether they will be okay with any other brand or configuration of ignition.
I also am only running Spektrum 2.4 modules on my JR 9303 using either AR7000 or AR9000 receivers.
I'm going to be the next. However, I'm running it on a DA-50 so I'm going to still use a regulator and I'm using the XPS system and soon the futaba system for a review plane / module sets. One of the greatest things about 2.4 Ghz is the frequencies are higher than the RF noise of the motors...