Just as a suggestion. If you used the SST software you could map 2nd gun to the 2nd stage of your trigger with latch.
In other words, say Im going in on a target and only want to fire my rockets. I pull the trigger just like Im firing my guns only Im also pushing in the pinkie latch on the lower inside of your stick where your pinkie rests.
Using that mode dial to cycle 2nd guns seems like a lot of trouble and must be slow. By the same token if I want to fire cannon only, say in a fighter or especially an IL2? I just pull trigger+Latch and the 2nd guns, always cannon, fire. When dive bombing I have weapons type mapped to fire button C+Latch so I can cycle to bombs and then drop them using trigger + Latch.
Even if you made up an SST profile with only that mapped it would seem worth it. Tho Im not sure what would happen if SST was active along with control panel.