Thanks for the reply,
However, I looked at that model while attending the Toledo hobby show. Problem with the 3GR is the 3rd channel is simply a switch, and not progressive. I believe that radio was intended for trucks with reverse, traction control, ON/OFF type situations. Basically, the third channel is useless to nitro boaters that are looking for the ability of mixture control.
I was at work when I posted the reply. Now, I looked closer at the notes on that radio and it says it has the same menu as the 3PM. Then, looking at the manual and seeing the all the different switches and trim levers makes it easy. All you would have to do is reassign the third channel function to one of the digital trim switches that come defaulted to trim the ATL or such. This is exactly what some of us did with the 3PM wheel radio to use a third channel needle. It is very simple, done through the programming (no soldering) and is covered in the manual. Only takes a couple seconds. It does not affect the throttle or steering trim at all, you simply use one of the other trim switches that's convenient to reach while running - your choice, since the radio has several that you probably wouldn't use with a boat anyhow.
There's a link to the manual on the webpage.