umm, sorry, guess you didn't read your owners manual. it IS against fcc rules to change the frequency your transmitter is on, if you have a crystal based radio. if you have a module based radio you can swap modules, but pulling out a crystal and putting in a different one is is illegal.

here is a link to the fcc part95 which governs this, section 222 in particular.
http://frwebgate.access.gpo.gov/cgi-...2000&TYPE=TEXT

and also section 645 which defines what a module is and isn't
http://frwebgate.access.gpo.gov/cgi-...2000&TYPE=TEXT


and finally, 653 saying that this has to all be stated in your manual
http://frwebgate.access.gpo.gov/cgi-...2000&TYPE=TEXT


yeah, people ignore these sometimes, but it opens you up legally to a whole bunch of problems. If you swap crystals and cause someone to crash, you might now be liable for any damages that happened. same with using 72 mhz to control a boat. if someone puts up a plane on the same frequency, guess what, you just bought yourself a plane (or millions of dollars in a lawsuit if the plane happens to kill someone)

also, do you have a link to the futaba site where it tells about using airtronics equipment? I highly doubt futaba is recommending doing anything like this. Even using a module from a different manufacturer is not legal, since it hasn't be certified for that radio. (common example is people using hitec spectra modules in a 9c. they work, sometimes, but it still isn't legal)