Tigger, to use the thumb mouse you have to be running the SST software. I found that the 52 works better without it, so I've never done any experimenting with it.
I always map my look-up to the pinkie trigger. It's much faster than using both hat switches. I have the upper hat switch set up for screenshots/film record/and dive flaps.
I don't know why the OP wouldn't use the throttle, opting for cutting the engine off by using a button. To me that just seems silly.