RE: quick question about crystals
No, you wouldn't be able to use the 72 MHz (H, not G) crystals in the 75 MHz radio.
MHz is an abbreviation for megahertz - or millions of cycles per second. The airborne RC equipment uses the 72 MHz range, ground stuff is the 75 MHz stuff.
It's not just the crystals in the radio, but there are other tuned circuits that may or may not work correctly, or even have enough tuning range to cover both bands.
Even if there were, it would take professional technicians and proper equipment to change from 72 to 75 MHz or vice versa. So it's not a simple matter of swapping crystals.
Besides that, in the 72 MHz band, it's not legal in the US to simply change a crystal to change your transmitter frequency. I'm sure people do it, but you're supposed to have the TX checked for proper tuning and frequency accuracy so that we don't interfere with other users of the 72 MHz band, or ourselves with improperly tuned transmitters.