I know, that initial width is one dimension which is simply not available in any of the tutorials I could find, nor is there a great pic of it. I seem to remember measuring 1" on mine from a set of plan drawings someone here did, then laminating plastic grips in two layers on top of that to simulate the trigger assembly. Looks good, and feels like it's a fit in my hand.
Dang, Superkrates beat me to it with REAL INFO! Cool, but is that the [plastic grip or the metal parts of the trigger assembly?