Lamar, I was promoting the concept of doing a factory endorsed mod to your Rcexl optical ign. switch. The mod involves the installation of a battery eliminator circuit (BEC), and it's done simply with 2 small solder joints (as shown in the directions) as mentioned earlier. Not sure if you aren't following, or aren't interested.
The mod would mean you don't need a separate ignition battery (NiMh or other), or a switch to turn it on/off? The ignition would then get it's power from the receiver battery.
After the mod, you would no longer need one of that pair of switches to turn the ign. on and off. That would free it up to give you an alternate power source in case of trouble with the first.
NiMh has developed/is developing a bad reputation among those placing high demands on their batteries. Not saying they're junk, saying if you're buying a battery, there's a newer generation battery available based on newer battery technology. Most guys find the more they know about them, the better they like them. Some insist, as your directions state, that as bad as the NiMh are, they're still better than Nicad, though I'm not sure I would agree with that..... -Al