So I’ve just fitted the above, trouble is now when I shift into the granny ring, it fouls the device. It’s an xtr m970 chainset with xtr rings with an XT BB and the mrp is BB mounted, 73 mm spacing. Any ideas??

Could be anything. Is it BB mounted or on ISCG tabs? Often when fitting a chain device, you need to fit/refit with different spacer combinations to get it to work without rubbing. Could be just a case of having a play about.

Where does it foul?

It’s bb mounted, using a 73 mm bb shell so it replaces the single spacer you would normally use. It fouls the chain when in the granny ring, to the point that the crank will hardly turn without a fair bit of force. I’m thinking that using one of the bb spacers between the driveside cup and the back plate of the device to give a couple of mm more clearance but am a bit worried that that reduces the contact point of the non driveside crank by a couple of mm. If I do this am I going to be killed to death?