Good news on the MIDI drift issue... the fix (for me) was so simple I am embarrassed I hadn't realized it before, but I figured I'd share as I know others have this problem and maybe it will help.
I discovered that drift was almost 100% eliminated if I had the BSII powered via the DC power supply... on my earlier post (scroll up a few) I thought it was due to filtering MIDI so only clock was getting through. Too much MIDI information may be part of it, but I realized when I ran those tests I had the BSII powered via DC.
When I went back to having the BSII powered via USB bus (attached to my PC) it would drift again. On a hunch I re-attached the included power supply and ran the same clock to it (first via DIN and then USB) and it stayed locked!!! I could still get it to drift, but I would have to introduce wild BPM swings to do it. If I kept the tempo locked or moved it +/- 10 BPM it seemed very stable.
Perhaps others didn't have the drift issue because they are running the BSII off DC power or their computer's PSU is able to supply a consistent level of juice to the USB port. Whatever the case, I finally am able to get it to lock to ANY clock I throw at it and I am one happy dude. All it took as using the damn power supply.
Hope this helps others!