Eliminate the duct tape, the print finished and the new boot slips onto the foot with friction lock between the layers. The Shop Vac fitting is ~1 1/2 inches at my inlet and is one of the tapered extensions that came with it.
I tried another cut without the bottom plate in place and a lot of dust was left behind. The new one should tighten things up and close some open holes to improve the suction. I also removed the lower black collar from the Dewalt to get more airflow around the bit. Having the bottom portion removable allows better access for switching the bit a well.
It’s too late to go play so I’ll get it attached tomorrow and see if I need to change anything else.
Edit: Here’s the Thingiverse link for this version. Labeled as ‘WIP’ until I mount it up tomorrow. http://www.thingiverse.com/thing:1875449