If your truck can do it, no problems, then why are you complaining??
A 2.6 isn't a big charger...no truck should be spitting and sputtering on a 20 mile drive, unless it's not tuned right. The only thing it could be hurting on the truck, is a 13mm pump...the rest of it, should be fine. If you're engine can't handle a 20 mile drive every once in a while, things are getting way out of hand
This is making me want to throw on a S465 and prove a point...although having never pulled before, I'd quickly be humbled by the sled gods! That being said, there is absolutely no reason a 2.6 truck can't handle 20 miles.
Chris