TRP Brakes

[Bean]

Hi,
The Allmtn 3.0 I have has TRP G-Spec brakes on, now the front are fine, but the back seem very poor. Have swapped to Shimano pads but not made any difference.
Pressure is there so doesn't seem to be air lock just no stopping power. Would a larger rotor (180mm) make much difference ? Weigh 195 lbs so admit I'm heavy but the wifes Levo with Guide brakes stops instantly with me on and the Allmtn just doesnt.
Any advice appreciated before I start swapping bits

 

[mambo]

I swapped to Shimano XT M8120 front and back and couldn't be happier.
My Allmnt Xduro 8.0 had the TRP G-Spec Slates and honestly they couldn't really handle the downhills.. the bike now stops instantly and I can get to the bottom of a track without much hand/wrist fatigue.