The small pulleys, made for 5/8" webbing, are behind the hipbelt, about 9-10" apart, and are anchored to vertical carbon struts in the pack frame. The webbing straps run back and forth, a la block-and-tackle (like a 'come along')from the pulleys to the sidearms, at a point on the sidearms that is close enough to the pack frame that the hipbelt will not rub on the straps. Although that does not provide much leverage to pull the sidearms together, the block-and-tackle arrangement exerts more than enough force to keep the belt pulled tightly around the hips. The sidearms must be long enough that their front points are sufficiently forward of the hips to not rub against the hips.
After running back and forth, the webbing runs through a pulley in sidearm, and runs along the outside of the sidearm to a buckle, so you can tighten the sidearms just by pulling forward on webbing running from the buckle on each side of you. It can be done while walking.
It's quite late here now, but over the weekend, I will try to take and post a few clear photos of the belt area of one of my packs so you can see exactly how they are set up.
Thank you for your interest.
P.S. That photo is of one of Jack's earlier prototypes, much cruder than the later models that had the sidearm tubes much closer together and a much narrower hipbelt, in two pieces with one end of each piece anchored to the center of the pack frame with fabric. That allowed the belt to rotate freely, resting on the crests of the hipbones at an angle. I have found that either one or two piece hipbelts will work, so long as they are set up to rotate enough around the attachment point at the small of the back. The slimmer sidearms work better because there is less chance of them rubbing against the rib cage or the lower hips. They are a little more prone to breakage than the large radius ones shown in that photo, but with reasonable care, that is not a problem. They can be kept closed up against the pack when it's not on your back.