I run Fibrax sintered with my Shimano bottom of the range OEM brakes (can’t remember the number, think it’s either 525 or 545). I think they’re great, never had any problems with fitting them and they last 10x longer than the normal Shimano ones. I’d definitely recommend them.
Slightly off topic but when I was in Morzine a few years ago I destroyed a set of ‘downhill’ pads in half a days dusty riding (technically my brakes aren’t supposed to be used with sintered), I swapped them out with the Fibrax and they lasted the rest of the week (and summer) without overheating. It’s too late now but ever year at the York Cycle Show Fibrax have a stall selling pads at under half price so I always stock up on them. Even at full price from CRC I think they’re still the best value pads around.