Well, it's likely that Chalie's bass is 1.65 inches thick, which is the minimum for regular Series I/II electronics. Distillates (and all non-Series neck through basses and guitars we make) are usually 1.55 inches thick.
It is possible to use the filter pots from the Signature and Distillate basses instead of the mega thick ones we use on the Series I/II basses. However, they do feel different (though no difference in tone). They are also a little shorter life span. So possible, but slightly strange.
I think on Jason's we did two different things - one was a very thin top on the first conversion. The next one we built up the backplate shelf to be suitable for brass (that gains 1/16 of an inch) and did less thinning on the front. You don't want the top too thin, because it becomes overly fragile.
