If I was doing turbo on a tow vehicle, I'd want to tune it by EGT and not just some canned tune or something that the local drag/street racer tuner shop can whip up. That 700hp turbo engine might have to be detuned to 500hp or so once you get it to where you can lean on it for long periods of time. Think old-school turbo engines with low compression and relatively large and laggy exhaust housings, which hurt power but are great for heat management.
Think of it this way: The engine as it sits is already tuned and rated for the kind of use you are putting in. The methods that people get to electronically add power (less enrichment, more timing) take away thermal margin because those tunes are great for the kind of people who AREN'T doing things like towing heavy trailers up mountains in August. You can get away with a lot when you're only expecting heavy load for a few seconds at a time.
That brings up a point nobody has mentioned: The fuel you are using. GM has, basically, two sets of timing maps, "low octane" and "high octane", and after every time the computer sees the fuel level go up a certain amount, it will switch to the high octane map, and if an excess of knock is noted, will switch to the low octane maps. Many of the "tuners" just copy the high octane map over to the low octane side and let the knock sensor sort things out. So you'd be able to get some of the benefits of a tune by just filling up with the good stuff when you have a trailer attached. (The high octane maps are also generally the MBT maps, so there's no benefit to going even more advanced)
