Kenferg1

Don't worry about it. Had a similar setup on my '11 EB, and I never had to slow down climbing the grades. And that was with 3.31 rear end. You are equipped perfectly to have an enjoyable trip out west. Have fun!

13EBF150

Morning .. I have a '13 Eco with the HD package and tow our 5er 90% of the time in the Southwestern Colorado mountains between 7 & 10,000 ft.
I always keep it in tow/haul mode. Going up hill I always cancel the cruise control so I can control the speed I want it go up the hills.
Going down the 6 or 7% grades, I slow the truck down to at least 10 MPH below the speed limit at the start of the hill and leave shifter in drive and push the button manually to start down shifting & to lock out 4, 5 & 6th usually down to 3rd gear and brake if need be. Have been times when I've locked it down into second to help slow it down. This seems to work great.

Milo

SkiSmuggs

I alway tow in Tow/Haul mode. It's what it is for. Engine braking is limited until it gets down to 2nd gear. No need to lock out or manual shift as T/H takes care of it.
Don't ride the brakes on the down hills, just maintain a speed range appropriate to the conditions, say 40-50. Slow to 40, coast to 50 and slow to 40.
I have towed Vermont, New Hampshire, Colorado and Wyoming without issue in a 2011 Ecoboost for 3 years before trading to an F350.