Now towing with a HDT, why didn't I do this years ago

^^^^
What he said ,we both forgot to answer your mileage question
Iam at 9mpg total for the summer,not as good as last year but MI and OH raised their speed limits and I spend a lot of time on I75,I used to get 9.3 or 4.
Here is where the enormous fuel tanks come in ,I can fuel in the lowest priced state and reduce my cost per mile to the point its the same as the 7.3 I had (with a smaller trailer.)