I'm going through this (in a way) with my xtx. I fitted Magura fat bars and risers with spacers. I tried going up to 40mm and just wasn't happy with the tight cables. Endedup using shorter riser spacers and some washers to shim up to where I think its at the maximum (apart from the clutch cable which I had to buy longer and fabricate a bracket). It was pretty frustrating.