RE: CDI ignition battery in receiver or direct from battery
It does mainly depends on the airplane weight I think, if you can use a separate battery then do it, if you can't then it can be taken from the receiver.
I use a 1800mAh for the receiver and a 1320mAH for the ignition and they last about the same time, we use JRR921s, a friend of mine went to the Rx directly to make the weight, the results were the same, so it's really up to your liking.
Regards