Jim, I had some photographs posted months ago. Unfortunately in the interim my computer crashed and I lost all of those images. My tubes are built from ABS (black) plastic componants. The sizes are 3" for 8X10 and 1 1/2" for 4X5.
The tubes for 8 X10 consist of a length of 3 inch tubing to which one end is capped with a 3 inch glue cap and the other end has a 3 inch male pipe adapter. The length of this assembly is 1/2 inch shorter then the long dimension of the 8X10 negative.
The next componant is a short adapter used for minimal agitation. This adapter consists of a 3 inch female adapter glued to a 3 inch male waste adapter.
The third componant consists of a 3 inch female waste adapter glued to a 3 inch glue cap.
Componants one and three are used for conventional development. Componants one, two and three are used when one does minimal agitation. The purpose of componant two is to allow full immersion of the negative in developer when the tube is placed on end for the "rest periods" for minimal agitation.
I also use fiberglass window screen material on the base side of the negative to allow the presoak water to access the antihalation layer of the film. This precludes the necessity of moving the negative in and out of the tube during the presoak portion of the procedure.
For 4 X 5 negatives the assembly is the same except for a reduction to 1 1/2 inch materials.
Hope this explains this to you. Good luck.