Diesel_Brad,
That load, the lift and larger tires, I think the 9mpg isn't to bad...... In my Ex, it is 100% stock, and towing the ~5000lb TT I get 12-14mpg, which puts me in at just under 12k..... so pushing 20k and if you were doing "Interstate Speed Limits" I don't think that is to bad.
I do love my 6.0. My Dad has a 97 Light Duty F-250 4x4 Extened Cab, Short Bed(Looks like a half ton, 7 lug nuts) with a 5.4L Gas and I have a 03 Excursion 4x4 6.0L PSD. I have the same power towing, as he does empty. He has a 23' Sea Ray that is ~5000lbs and I ahve my TT that is ~5000lbs. (I know they tow completely differently even thought they weight the same.....) His truck, pulling the boat feels like it is really working when running 65 in 3rd gear (OD Off). I put mine in THM and set the cruise with traffic and it just purrs along.
I test drove the Enterprise before Trav bought it, and it was ..... well and N/A IDI slow, and I have drive an 96 OBS PSD F-350 4x4 RC LB that is a FD Grass Truck and it is 100% stock and has a 500gal water tank and a portabel pump in the bed and it is ...... we slow.... I love my 6.0 and would buy another one without a second thought...... they are not as bad as everyone trys to make them sound......