Found out, I have a 6” inlet on my Grizzly 3HP dual bag dust collector, not a 7” like I “assumed” I had. Luckily, I have 6” HVAC parts to use up for today. But it did force me to redo hastily the top plate from 7” to 6”. I also cut out a 14” with 45 degree bevel for a temporary plate used to fine tune the chimney height, for future cleaning of interior lexan, and if I decide to go forth with the bellmouth it will be easy to install.
Here is the latest picture of my progress. Nothing is sealed, siliconed, caulked, or grey pastey stuff on the HVAC duct work. And yet.. when I fire it up, it works :) Tossed a handful of planer shavings in and to the eye.. it appears 100% of the shavings made it into the barrel.