Oh dear.... I'm thinking you might want to move to a 72MHz channel. I'm not sure what the AMA says about it, but using a surface channel for an airplane MIGHT be enough to invalidate your insurance... not sure about that, but it might be worth looking into. Secondly, it could raise the chances of you being "shot down" by a car/boat etc on "your" channel. The car guy down the road might see an airplane, but won't worry about shooting you down cause you're on a different set of channels...

Most transmitters can be tuned to a new channel relatively easily (by the manufacturer)... I'm sure somebody who flies Futaba will jump in here. The receiver can USUALLY be retuned just by stuffing in the appropriate crystal.... although going from 75 to 72MHz may mean having to send the receiver in for retuning as well.