I've seen this in the top of the thread list lately but was busy on a couple of projects to look. I've read it all.....interesting threads should be read to see how you get to what you jumped into.
Looks like it does work. I'll have to give this a shot. Been doing the PTB. To many small topoffs if not readjusted alot but works well.
Over cutting the size for the single layer will work if the sides are cut tapered. The widest part of the taper is thinner and will compress forming a good seal while leaving the middle virtually uncompressed.
As I read the thread all I could imagine is that the Slug is really a custom fitting edobit!
Basically a constant feed sponge type of unit. No reason it shouldn't work well.
Nice job and follow up.