My Trident is 1 3/8" in diameter. Checking the specs of other popular pistol cans the diameters range from 1.25" to 1.38"
Measuring from the back of the barrel of my 226, it is 6" to the shoulder where the recoil booster meets the suppressor body. I know the Multimount is almost identical in size and length, so someone with one of those on a similar sized pistol should need the same clearance.
"No, it's not a silencer. This little doodad is my own invention. I call it a loudener." --Sledge Hammer