all this talk of 36 tooth 9spd sprockets has rekindled my interest in going 2×9 but I don’t really know the best way to do it. With a 36 cassette what chain ring sizes would I need to fit an XT chainset and still give a range of gears? Could I use existing shifters and just use the limit screws to keep real changes to just 2 at the front? Would the existing SLX rear mech cope with the larger cassette?
Advice appreciated.

If you are going from triple to double, rear and front mechanism should cope. I’ve got a 24 / 36, with a 34 cassette and have a good range of gears for most places I ride…