do you have a centrifuge of any sort?
1lb/gal comes from the amount of solvent required to cover the material. you can get a little more in there if it’s milled rather than pushed through 1/4" screen to break it up.
if you don’t have a fuge, getting the next 10lb’s in there is going to be more difficult, because of the amount of solvent you leave behind (15% or more)… going a third time will be even harder.
there are at least some folks who are having trouble getting 20lb into 10gal even with a fuge.
I haven’t really had the opportunity to routinely throw high THC material into a fuge in a couple of years, I mostly deal with 10-14% hemp biomass. There I can get 50lb into 15 gal extracting 10lb at a time (so going 5 times) and maintain the same (85%) extraction efficiency for all 5. the 6th & (certainly) the 7th were not as efficient. So I stopped at 5. that’s at -40C
going warmer, you can get more cannabinoids in to the same amount of solvent. I’ve seen good data on 1lb per liter using 20% THC material at about 5C, and may have pushed it a little further than that while helping out in a buddy a couple of months back.
I do however calculate how much solvent I’m losing to the biomass, and have a “make up” tank on hand to chase the last of the (increasingly saturated) solvent out of the biomass.