Obtained a .750 diameter x.125 walled extruded aluminum tube (Got a rod also, but tube has almost the same strength and is cheaper - $6.65) 33 3/4 inches long. Moved the two filament roll support arms to interior surface of outer frame. Cut 2.5 inch sched 40 PVC 7 3/16 inches long and one 1 inch long. Put the same rubber caps on the end of the rod to secure it. Sprayed rod with drying silicone lubricant and assembled. Works great. Coefficient of friction is much lower than with conduit. Could also store two additional rolls on rod with a couple of thin spacers.
Filament rack mod for 15 lb rolls