I've been using my IC-706MKIIG on aircraft com for a couple years now and works fine. (obviously for test purposes only)
The bandpass filters on the Tx driver stage has a pretty severe rolloff down at 118 mhz, but you can still get 0.5 to 1.5 watts out to the antenna and with a tuned antenna, -works great. See Jose Monroy's writeup at: http://www.aircraftdelivery.net/ferrypi ... rplane.pdf
He does a little pwr out check in the last couple pages.
I've done a couple of HF installs similar to his, but with a trailing wire antenna, and with properly integrated audio wiring (using the aircraft audio panel and headsets). I'm planning on a trailing wire system on the Highlander, but I've got to get it flying first!