I'm also in a holding pattern with my drive upgrades for now. 
I finally got around to my first tower upgrade but hit a small snag. I had ordered the tower kits without the sprockets and chain as I have lots in stock from all my fiddling about with these drives. However, as it turns out, the Weaver/P&D top sprockets are too large an I/D for Kelly's top shaft. That's because the Weaver/P&D steps up in diameter between the knurled section for the UJ yoke and the knurled section where the sprocket fits. Kelly's shaft, bearing and locknut design is far superior imho, but has constant diameter.
So the key point is you need 1/8" bore top sprockets, not the 3/16" ones that fit standard Weaver/P&D top shafts. You will get the correct sprockets if you order the full kit from Kelly of course. If you need just top sprockets, you can order sprockets from Stock as I have just done, using the part number Kelly was kind enough to send me:
A 6M 7-120804 0.1227 Pitch, 8 Teeth, 1/8" Bore, Plastic roller chain sprocket
Hopefully they will get here in time for my "6-loco Holiday Upgrade Extravaganza." 
Pete
