When I bought my 4x5 enlarger, it came with the wrong length enlarging cone for my lens. Not happy with that, I ordered a second wrong-length cone from Classic Enlargers ...just for the fun of it, apparently. Finally, I ended up making one out of 3" PVC sewage pipe that's attached to the enlarger by way of a metal flange you screw a toilet to. The upshot is that 1/4 of my enlarging setup was already meant to have crap flowing through it.
Well that's better than my setup which has crap flowing through it 3/4 of the time.