No buckle?
Check out my whoppie sling belt on my Mantis. If you're familiar with amsteel, this is super easy to make, plenty of great youtube videos if you're not.
Not gonna lie, I didn't measure anything. I started with about 5 feet of 1/4" amsteel. You'll want to get a couple D-rings and tri-glides to fit that webbing (looks like 2" on the Kestrel. Its 1" on the Mantis). Amazon had those. All together I have about $25 into this mod. I did have to cut the ends off the webbing, but this is as close to a non-permanent buckle delete mod as I could get.
Its solid when pulled tight, just milk the bury a little and give it a tug (like you're trying to stretch your pants before Thanksgiving dinner), it won't slip or move at all. One handed to tighten, two to loosen. I've put some miles on it the last week, and it stayed tight the whole hike.
I'm certainly thinking about covering this more in depth. I haven't seen this anywhere else. But like most of my million dollar ideas, if I think of it someone else has already done it.