[bpassmore]

"What I would like to know is this: on-road, with locked hubs (drive flanges still installed) and an open center diff (not 2wd or true 4wd) what is my rig going to drive like?"

It will drive normal while you go straight, then when you start making turns, your will feel binding and friction.

Eventually you will get a stress relief, either from a wheel spinning free, or from your birfs, or drive shaft or tcase gears popping.

i did this on a 1974 Bronco. I had a dana 44 front end, and after about 2 miles, the steering was so hard to turn the i had to start backing up.
I got to a point where I could put the Dana 20 tcase back in neutral, albeit with some great force.

I later had to drive in 4wd again because of a tcase lockup (i can only assume from the damage created in that test), and this time i popped a front ujoint (no birfs).

Short answer, it will get real hard to steer, it will get really bound up in the drive train, and you will break something. It wont take long.