[HO455]

I went and looked back at photos and posts from when I first got my Burban to see if I could find anything more to help you. It had very similar, if not the same bags you have. They were mounted slightly differently on the top, but the only real difference is that mine were the thickness of your upper plate higher i.e. they had welded a plate flush in the upper spring pocket. The lower end was just bolted through the center of the factory control arm with a large washer on the bottom. With the exception of the bumpstop/steering stop being removed the lower control arm was unmodified. So in essence the top and the bottom of the bags were closer together than yours are when aired out. Giving mine more useable lift. The front bumpstops at that point were the ends of the swaybar. My truck doesn't have dropped spindles on it and it has smaller diameter wheels so when it was sitting on the ends of the swaybar the bags were really compressed. Where yours is hitting the fender wells because of these differences I would venture to say your bags are not as compressed. (Photo #1 is the bag aired out)
In this configuration it took 140 psi to get the truck up to ride height. (Photo #2 is the truck at ride height with 140 psi in the bag. Notice I was only getting about 4 inches of lift))
I fabricated a pair of cups (The ones pictured above 3" if I remember correctly) and after installing them it only took 90 psi to get to ride height. Which was a relief on the poor old air compressor since I was able to adjust the shut off point down from 175 psi to 135 psi. That markedly reduced the run time of the compressor.
All this being said I believe your problem is the bags are too short as installed to get the necessary lift. So your options are, install some cups on the bottom or spacers on the tops of the bags, or replace your current bags with ones that have a greater operating range. I suppose you could also get shorter wheels and tires and stock spindles, but that seems too much like going backwards.
Unfortunately I don't believe there is an simple adjustment or lubrication process to solve the problem. I would go with some cups ( They are inexpensive and effective)) then after installed drive the truck a couple hundred miles and so then you will know if you want to shorten them up a bit to dial things in better.