Thanks to all for the replies and help! I am planning to do some experimentation this week, probably leading to having the TPMS sensors installed in the new tires eventually.
Just to cover some things mentioned:
Pressure: Actually raised it to 35psig in the new tires to see if I could improve the MPG-no significant change.
Alignment: New alignment with new wheels/tires, plus a recheck-no change.
Direction: New tires are directional-proper direction.
Weight: Possible increase, I will check. (doubt this would have much effect, especially "over the road", once up to speed the effects are minimal.)
Driving style: Again possible, but the "OTR" (highway) numbers are mostly with cruise on and it still goes down. When I first noticed the reduction, I figured that it was my being more agressive, but after a couple of thousand miles, I know it isn't.