Where did you get 72° from?! That's massively OTT for a leg - you should be aiming for something around the 60° mark.
Shoulder is the far tougher cut to cook, be that sous vide or otherwise, so you either aim for the same 60° and cook for a lot longer (20hrs works well) or go higher but for a shorter time. I've done shoulder at 76° for 8 hours and it was superb.
A few recipes online but I was pretty hungover and anxious to put it in the water. Excellent, thanks a lot - I'll try that tomorrow - it's only a kg bone in so should i be looking at reducing the time (no idea what the max thickness is yet)?