I want to use my Century Wide Angle adapter
in conjunction with a couple of Tiffen screw-on filters - only problem is, the threading on the
WA Adapter is too shallow to thread onto the
lens with the filter(s) in place -

Anybody know of a jeri-rig and/or work
around for this?

Your Century wide angle actually comes with filter threads on the front?

NO - I want to be able to screw the filters onto my
XL1 lens AND THEN mount the WA adapter (72mm)
on top of the whole shootin match

That's not a good idea. A matt box would be the better solution if your wide angle doesn't have filter threads on the front.