StickyShisha,
If you only plan on running 7g-14g amounts through it, the sstb is the tube to use! A tighter packed tube will actually yield better, although the tighter you pack the more you risk causing a blowout. The rule to focus on is that the tube must be evenly packed throughout, from top to bottom. If the tube is packed more tightly near the top (closer to where butane enters) than it is at the bottom, the material can shift downstream and cause it to all blow out the bottom.
That being said, tight packs will give you the best yield, although 1.5 grams from 7 grams is a very good yield. If you've got a scale and can accurately measure your results, producing between 15% of your starting weight is considered "good" and 20% is considered great.
Yield is mostly a factor of the strain you are working with, and the quality of the material.
If you only plan on running 7g-14g amounts through it, the sstb is the tube to use! A tighter packed tube will actually yield better, although the tighter you pack the more you risk causing a blowout. The rule to focus on is that the tube must be evenly packed throughout, from top to bottom. If the tube is packed more tightly near the top (closer to where butane enters) than it is at the bottom, the material can shift downstream and cause it to all blow out the bottom.
That being said, tight packs will give you the best yield, although 1.5 grams from 7 grams is a very good yield. If you've got a scale and can accurately measure your results, producing between 15% of your starting weight is considered "good" and 20% is considered great.
Yield is mostly a factor of the strain you are working with, and the quality of the material.