On all of my stage regulators, I use those small screw-in spg's that are the equilant size of approx. 10 dimes stacked up and thread right into any high prossure slot on the 1st Stage. I rarely ever have to look at the spg, but it does come in handy from time to time - inexpensive, non-obtrussive and handy.
I agree, those work really well. In fact at the shop today we were 50/50. half of us don't use spg's and half use small or "button" spg's. The conversation was migrated into more of a preference for having a gauge, but not really needed if pre dive checks were performed.
Cheers