Cooper STT Pro sizing

I went from 33x12.50 BFG KM2's and these are unbelievably quiet. The Jeep does seem to squirm around a little but I just had them mounted last night and only put 10-15 miles on them.
 
I went from 33x12.50 BFG KM2's and these are unbelievably quiet. The Jeep does seem to squirm around a little but I just had them mounted last night and only put 10-15 miles on them.

What do you mean by "squirm around a little"? Does your jeep wander back a forth a little on the hwy?
 
I was gonna suggest you check your alignment, specifically caster, but you could be right and the softer tires are squirmy.
 
Your toe being off or not enough caster could cause a wandering effect. Does your steering wheel return to center on sharp turns?