Way back, a chap who lived two doors down from me was a radio techie sort, he made/modified more or less anything to do with radio control. He had a go at modifying a heli gyro for me to install in my Patrick Henry, but after many attempts and much bad language, he could never get it to work properly. It just wasn't sensitive enough, so in the end it was binned and one of Ron Perrott's SALCONs was installed in the boat...what a transformation!
The chap in question went on to build a whole series of 40mHz radios, from simple two channel sets up to hugely complex eight channel outfits with variable this and adjustable that, superb things they were. He modified my Futaba 6 channel outfit to have slider switches for the ballast tanks, upped the output of it, and all sorts of things.
I believe I'm right in saying that Skip Asay over in the US of A made heli gyros work properly in a sub, somewhere I have a magazine article of how he did it. If I can manage to find it, I'll scan it and post it up on here.
Rich