Big tubes do not lose yield. It's a myth. Unless I have some out of the ordinary shaped tube...Maybe mine funnels the butane down through the material better than other big tubes out there I dunno but I consistently yield between 20-28% back on good bud material. Same yield guys get with any small ID tubes.
LOL I gots 4 of them bad boys midnite!!
When we were running open tubes, we got our best yield from the smaller ones, but under an inch ID is such a pain to load and unload, we standardized on one inch.
Now that we are running tubes that soak the material, rather than washing by it, we see less difference.
I did add a top flush line, so that after the final dump, the enriched solvent can be rinsed from the plant material, and if you measured that step closely enough, there should be some difference, because butane flowing through a tube using gravity, finds the easiest way through and doesn't wash evenly, especially at the top of the column, where the butane may not even touch the material surrounding the injection hole itself.