I know of at least one crash on 72 on the first flight with the CDI plugged in directly to the receiver.
I would not fly with a CDI on 72 or or 50/53 or 35 or any HF frequency.
I used the CDI as an excuse to change to 2.4g from decades of trouble free flying on 53.
I plugged the CDI directly into the reciever with a suicide extension....it is a standard servo extension.
When at the field or when I know I am going to run the engine, it is plugged in at the CDI.
In the shop or with the receiver on at any other time.....the extension is unplugged.
No second switch, no extra batteries, no second regulator.
One thing though.....the receiver battery should have more capacity than usual because the CDI pulls a fair amount of current.
The higher the rpm, the higher the current....
I am using the Futaba 6008HS receiver with a 9zap transmitter and matching tx module.