Replaced the flex duct today, and while it was down, stuck two layers + GG between the joists where the duct was. Finished putting up drywall and GG in all the joist bays, and then put more insulation in my rim joists. I had sprayed it with foam that gave me R14, so the fiberglass was overkill, but I had a few rolls left over that were too small for 16 OC walls. So now I'm ready to spend tomorrow putting up my walls. A bit intimidated for some reason, since walls seem so permanent, but after doing some demo with a sawzall at a friend's house, I know nothing is permanent.
Also realized I went way way overboard in applying GG to the drywall between the joists. Somehow I used a full bucket. That sucks since it's not exactly cheap. At least I can't hear footfalls right now. I had my daughters running around upstairs, and could barely hear them. When I insulate the joists, and put the 2x 5/8" GWB and GG, I doubt I'll be able to hear an elephant up there.