I don't know what the overall height limit is for you, Chucks Volvo is 13'-6" with a dropped roof for his 2 AC units. That's as high as I'd ever go. My height limit is set by a 9'-0" Garage door to store my rig, right now she is 8'-10.5" Because of the spread on my axles and the dropped driveway I clear the door with 2-3"
About the fuel milage, I checked it returning home from Watertown, 150 miles straight into a 15-20 mph headwind.I was getting late,so I set the cruise control at 73-74, that way I wouldn't have to pass anyone. I had a little trouble fueling it up all the way with the big truck nozzles, so I don't think I got a good test of the fuel economy, I put 151 miles on it and put 17 gallons of fuel, so 8.88mpg
I'll try again next run out, next time I'll use the small nozzle fuel pump and take my time to let the tank burp out the bubbles.
I'm also going to recap my Michelin XDE's in the rear, I should pick up almost 1.5 in tire dia over my bald XDE's that should help drop my RPM's just a bit and still maintain my 75mph cruise speed.
-blizz