Hi there, I have had occasion to re size my vest significantly.
I purchased my vest weighing about 218 with a 36" waist....Then after a run of the P90x workout program, I weighed 178 with a 32" waist. My Klassen vest which was made for me in particular ( Dual Mount, Low profile Arm, Hinged on one side) Was completely closed and was still very very loose.
yes I could have added more padding, but it would not fit the same, The sides of the vest were too long. I literally am smaller front to back , so I went to WK Fx's in Toronto. Walter measured me and cut 1/2" off one side and I believe 3/4" off the other side, then re wrapped those ends, re drilled the holes for the hinge on the hinge side, gave the vest a good once over, installed the Triax holder bracket I wanted and sent me on my way.
Fast Forward 2 years....I had gained about 15 pounds and the vest was a wee bit tight. I ordered the hinge spacer and all is well again. I have since dropped 5 of those pounds. So I'm good to gain another 5-8 or loose another 10-15 and be fine.
So...you can loose tons of weight and get it pretty much cut down on the sides, but not gain it back if you do.. Good incentive!