Propane Vs Butane Yield

My friend did a run on a closed loop with propane being fed top drip style.

19 pounds of solvent was run through a "5 pound" terrp tube 4x48" which holds around 2.5 pounds of material.

Yield was around 4 ozs of lighter than usual oil, 2 ozs sauce and 2 ozs isolate.

Then to check how much the propane didn't pick up, he ran 12 pounds of 70/30 butane propane mix through the same tube and it yielded around 42 gs prepurged.

It would appear a heavy propane run is still leaving behind a good amount of oil somewhere around 20% of the total yield =\
I suppose it would be scientific to do another run with the same amount propane then try to do a second run using the propane but I would guess it wouldn't pick up as much as the 70/30 mix.

Expected yield was 5-7 ozs using one run of 70-30 mix, and total yield should be right around 5.
In my experience N butane definitely has higher yields than propane and ISO Butane. 100% n butane has been my highest yielder, but there's just no pressure at negative temps. I just switched from running 50 nbutane/25 iso/25 propane, to 60/20/20 and my yields went up at least 2%. I ran 70/30 for years but recently switched to ISO because it has a higher pressure like propane but yields more similar to n butane, and it seems to make things more stable. I think next I might try 70% n butane 30% ISO butane. Hopefully I'll still have high enough pressure at low temps with out propane.