I have the cabinet covered on the back side down 16" from the top, as are the sides. The top is also covered, all of this with 3 1/2" fiberglass R13, density 1 lb./cu.ft. (as nearly as I can surmise from the sources I've read).
I am driving the 416b with a JBL/UREI 6290, 300w.@8 ohms, damping rated at +200. The response is very good, it's definitely digging low but I think I can get it a little more lively than I have it by removing some stuffing.

For some reason I abandoned the toggle "clicker" device. I'll try that out tonight. Drapes are sure to be hung, along with some type of shade. Her Highness has a thing about daylight in the Palace.