Cruise control on manual

I have a manual transmission 3rd Gen TRD Off Road that I use to pull a 3500lb loaded travel trailer.

The owners manual says no cruise control when towing, but have you guys gone against the recommendation at all here? I’m mostly towing in flat areas at lower highway speeds (55-65) in 5th gear. I just thought want sure why I would cause any harm if I used it? It sure would reduce some fatigue.

 

With a manual transmission on flat straight highway it shouldn’t be any problem. Even an automatic on flat straight highway is not a problem. Wouldn’t use cruise control on a winding road or while on mountainous roads or grades while towing.
I’ve used cruise control a couple times while towing my boat but I really just don’t feel comfortable doing so.