Without weight in the back of the truck, towing with the extension is a bad idea as posted above. Once you have 3 tons or more over the back axle it reduces much of the negative effects.
I have told people they can make towing solutions that are less expensive than Torklift's, but they will not get the lifetime warranty or technical support that exceeds that savings. I also have more than one trailer I tow and other times I use a cargo basket off the extension. It would have been cumbersome and cost prohibitive for me to modify all the things I use so that I could connect directly up to the receiver.
As a rule of thumb, you should have enough cab height clearance if the underside of your cabover to the bottom of the camper is 4'. Don't forget to take the additional height of cab clearance lights and cab mounted antennas into your measurements if checking how clearance you need. I used 3/4" thick horse stall mats on my bed to clear gooseneck hardware that protruded up - These wear well but are heavy. There are lighter solutions if you need additional height to clear bed hardware or the truck cab.
