Well I finally got around to doing a serious session of fiber 20x24 in the 3063 drum, flawless! I trimmed off about 2/3rds of an inch off the 24" side and then lined the paper ends up in an area of the drum with low ridges versus tall. No buckling, no corrugation, no problems. In fact because the paper gets so wet during the pre-wet and is a longer processing time, I feel it is far less prone to streaking and looks beautiful.
And as far as washing, taking some of the dividers out of my 16x20 Eco-Wash worked great, 4 prints at a time with a gentle fold and it's all good!
The drums rock!