Here are a couple of pics of the hitch I put on the back of my M936 this past year. I can back into about any vocational truck, or probably tactical too, and within five minutes have the disabled vehicles tires off the ground. For most "civilian" trucks, the hitch legs ride about level. I would guess that on a tactical truck the legs might run a little downhill, not nearly as much though if the legs were attached lower on the wrecker (ie; shackle points or pintle). I usually put some cushion between the hoisting bar and the bumper (more if it's a nice bumper), chain, lift and go (after dropping driveline, attaching air hose/cage brakes, hanging tow-lights, ect).
One time I was pulling a truck from the rail-head to NTC soon after it opened with my M543...had the tow-bar on the front bumper shackle mounts of the disabled truck and picked with a 5/8 chain, tires a good foot off the road...as I was cranking down the road at about 50, a little old lady backed out of her driveway about a 100 yards ahead of me...I put the brake pedal to the mat, looked into my mirror to see the disabled truck running up into my crane hook. When the truck came down, it caused me to pull a 40+ MPH "wheely". I did not hit the old lady, but I think we both had to change drawers afterwards...from then on, I got into the habit of always using the axle vices when on public roads while CC towing.