I personally wouldn't lift too much if I ever planned on towing because it changes the geometry of way too many things on the truck IMO.
First off a Class IV hitch with a 2" drop hitch, and a 10 k trailer (a relatively standard set-up) puts the moment arm point almost in line with the trailer hitch creating very little torque (T=F*D if D is almost 0, then T is almost 0, obviously your trailer hitch sticks out a few inches behind the back of your truck so this is not perfectly true...) if you have to slam on your brakes (like you inevitably have to do when some moron cuts you off). Add an 8" drop hitch to that like the one myyoung84 has in adjacent thread and suddenly slamming on your brakes creates a lot of torque. Basically though your truck stops from 60 mph in (130+/- ft I think somewhere about there) which is -9.07835 m/s. 0^2=26.8224^2+2*A*39.624 where 26.8224 is 60mph and 39.624 is 130 ft in meters (sorry I actually like to use intelligent units... lol). Throw in your 5k trailer (let the brakes do half the work) and we know the force the trailer exerts on the hitch is F=m*a, m=2267.96 kg*9.07835=20,589 N. T=F*d where d is 8 in and you have over 3000 pound feet of extra torque on your hitch. This isn't even taking the static loading and tongue weight of your trailer into account, and we all know tongue weights gets really really high when you slam your brakes. This **** scares the engineers that built your truck's chassis, and hitch every time they see you driving down the road.
This is all not even taking into account what happens to your tall ass truck when everything starts fishtailing.
I am not opposed to lifting, don't get me wrong, I just think that if you lift your truck you need to be very conscious of the stresses you are exerting on the components, and make smart choices. Towing a camper or something will probably not get you into any trouble, but do keep in mind all the factors at work here.
All my trucks (minus my pissant 1500) get used for goosenecks anyway (the best way to haul real loads IMO) so I never do more than a couple inches of lift with a set of tall tires, but even then a squirelly bumper pull is not fun lol