I appreciate all the thoughts and help folks. Will be giving Monteagle another shot in 2 weeks and will let her rip with a bit more comfort from the input here.
I suspect on the eastbound run she'll aim for 5500 but instead of letting it sustain itself I may try to get it down to around 4500-5000 as its a pretty long downhill run- a good 5 minutes plus on the eastbound grade. She just screams at 5500 and its a bit disconcerting even though she doesn't red line until 6K RPM. I always use tow haul but may try without cruise control and a manual downshift to 4 or 5.
I've noticed there is quite an RPM spread between 3 and 4 -- more so than other gears. All in all its the best tow vehicle among 4 or 5 towers I have owned. (Certainly better than my old diesel that just ran as fast as she could downhill with no engine help!)
Rascal Joe