Here are my tubing notes
Rack tubes
1/4 x .028 handlebar racks
3/8 x .035 Porteur and rear
some people use 5/16 instead of 3/8 for connecting bars.
Stem tubes
.065 and bore it out to a perfect fit for the steerer.
1.375" .058 for 31.8 bars
1.125" .058 for 25.4 bars
1.125" .049 for 26.0 bars
stems 90 - 100 mm for under 150lb riders . I use 1.125" .035
stems 105 - 120mm all weights 1.125" .049
all 1" ext stems get .049
all lugged stems get .035 ext. I turn the material for the lugs to .035 thick from either .065 (that has been bored) or .058.
frame tubes
1 1/4 x .058
Mixte tubes
1/2 x .035
People I know seem to be happier with the tubing from Aircraft Spruce. Dillsburg is cheaper for a reason, unfortunately. The stuff I got from Dillsburg is ok, but I know people that have gotten tubes with horrible surface finish from them. You don't notice until you clean off the tube either, because it's covered in grime.