New guy here. I am also overhauling a surplus ILBE pack. I took it and myself on a shakedown short weekend trip and learned a lot about me and the pack.It had been 15 years since I backpacked. We both need some work, and both could stand to cut some weight.
After the trip I cut off the hypalon on the lower sides, and removed the tubing from the zipper pulls. After another trip or two I will probably cut off the beavertail and some PALS webbing. I have modified the load lifters by cutting the row of stitching below the top of the stays. It helped, but my next plan is to remove some extra length off the webbing where the upper superloc attaches. This should help get the angles better for a functional load lifter. Some of these ideas I got from this site, some from other sites.
I have also since added the PB. Seems like a great addition. I will probably through some weight in the pack tomorrow and see what kind of difference it makes.
Since having this idea to go backpacking again, I am down 20 lbs, my pack down just under 1 lb, and I have identified another 7-9 lbs to leave home next time. Progress.