I got to work on this some more today. I realize I should probably name this thing as it's a keeper. Any ideas?
I started making templates to install the lower bowl daisy wheel vents. One interesting thing I noticed is that the WSM vent holes in the kettle are larger diameter than the holes on the vent. So I likely don't have to worry too much about the alignment tolerance for the 5 holes on a 22.5" wsm vents. I have a few old vents here that I'll use for test fitting but I'll likely order new ones so they fit nice and tight.
One thing that I test fit for today that I didn't anticipate is that the wsm charcoal grate is 18.5" and the performer charcoal grate is 17". Damn, more work to do. I'll do the math and figure out which diameter/height combo can hold the most charcoal. I'd be up for a taller, but narrower stack of charcoal if that means longer burn time and more consistent temps. I always find that the fire in the wide/shallow charcoal ring of the 22.5" wsm moves around and fluctuates the temp a bit. I'm also lazy and try to control the temp with one lower vent.
My backup place is to drill new standoffs in the bowl to take the wsm charcoal grate.