It sucks. I am running 14" rotors with gigantic dodge floating calipers from a 2014 3500 or something. Still sucky.How's your braking with the one ton axles and the GM MCs? What about hydroboost?
Master cylinder / caliper piston sizes are a zero sum game, you just need them sized sufficiently to not exceed a certain workload.
Bigger rotors/swept area can make an improvement with no downsides (other than the need for more heat dissipation) so that's a win.
But at the end of the day, I believe the booster is insufficient. Hydroboost is neat but I'm a bit worried about the flow requirements of the downstream box/piston for steering. I would like to see universal electrohydraulic boosters become more mainstream. The one in the 100 is ridiculously better even with the stock master cylinder size than everything I've done to the 80.