Here are my thoughts:
It depends on what brand you are wearing. some brands are tighter than others. As a general rule, the roomier glove goes on the inside so that it doesn't slip off while working (if the outer glove is too big relative to the inner glove, it will slide and you'll end up with the glove fingertips off your real fingers making precision difficult. Thus, I use +0.5 inside, normal outside. Occasionally I have to bump everything up the outer 0.5 as well if all they have are the extra thick ortho gloves for the inside
I also recommend using two different colors whenever possible (i.e. brown or green on the inside, white on the outside so it is obvious when you puncture your outer glove.