<font color='#000080'>Hi
There is no need to put Orings or different mouthpieces or any other such things. There is no guarantee that you will be able to distinguish these with thick gloves. Again, if there is zero viz which prevents you seeing 3 inch numbers on the cylinder I do not see how you can see your depth to determine a switch in which case you wouldn't do one until you could see your depth (and therefore see the cylinder). In cave I could believe it (which is why you don't take cylinders in cave below the MOD) but not in ocean. The DIR method is that if the reg is not in your mouth then it is stowed on the cylinder and the cylinder turned off.
By keeping all stages/deco bottles rigged the same means that you can swop them around and always have the same procedure. KISS
Andy