Gary, the pressure drop in 3/8" tubing is SIGNIFICANTLY lower over longer lengths than typical airline tubing of 3/16" or 1/4" diameter. The relationship of tube ID to pressure drop (per foot) is NOT linear. Its something more like logrithmic or exponential. So as your diameter gets smaller, the pressure drop will increase drastically. 3/8" is right around the "breaking point" for air at moderate flowrates, so it doesn't surprise me that this has worked well for you
