I posted about the mods and radio setup I did for it sometime last year, I'll dig it up if I can. Short version is that I installed 2 push button switches on the left side of my radio and wired them into the 3 position switch on the DX6, basically making it fully up or fully down as far as the radio is concerned.

Then I set up the radio to limit throttle UP to about 75%... so now full up-stick and left-right is turret elevation as far as the Clark board knows!! Once that was working I just programmed the 3 way switch to simulate the positions of CANNON FIRE (full up throttle) and MG FIRE (Down and Left). As it works now I can fire the MG and CANNON via the buttons on the rear, or with the switch which still works.