-- Speaking as the one who started this thread, I got my answer to put the treaded tire in the front. This is not a knobby, nor is it a "reverse tread" rain tire, but just a regular bike tire with a modest tread like what used to come stock on road bikes.
The only spills I have taken were in patches of sand on the road and I was mining all the expertise out there to see if anyone else mixed tires on a road bike with good results through sand.