Again, I cannot address all these tech numbers, but David, you mention strong cross winds, and I can address that.
UNLESS you are driving Montana in 50 (or more) mph cross winds, I doubt you will feel em! With our TT and with the boat (both of which I pull(ed)) I can tell you, much over 35 mph cross and I am white knuckled, clenching jaws and very tense. Montana, being a 5er, and being Montana, tows very well in wind, even cross winds. I NEVER feel a 18 wheeler when they pass us on the xpressway, even if they are driving real fast, there is NONE of that push and pull that you experience with a TT or the boat. With the TT, it used to feel as if the 18 wheeler was going to whip the rear end of that TT around to meet the front end of the van/truck we were towing with. Did not like that. NEVER have had that sensation with Montana.
Now, you will feel it in your mpg of fuel useage. Many of us in the RGV, when asked when we are leaving for the north country, will respond, when the wind is out of the south!! We want it to push us out!
One year we left with a 35 to 45 mph head wind, and it killed our mileage, from 7 to 8 average down to under 5.5! That hurt!
Also would suggest, that if you have any choice, that one might be wise to NOT run if the forecast winds are for more than 45 or 50. We have heard a few horror stories of 5ers getting tossed on their sides in 70 and 80 mph winds.
As far as driving down hills, we have the Allison, Al has been teaching me how to brake enough to get the Allison to kick in and roar and brake us down the hill. The way I understand it, you need to learn the tricks of driving your truck, gas with or without Allison, or diesel with whatever trans you have. I am still learning, but I can tell you, I LOVE that ALLISON, specially on the 75 heading north into Cincinnati! Goodness it roared, but, I held to 55 mph with very little application of the truck brakes! Whaoooo, I am ready to try that again!
Again, this does not directly address the subject of the original question/post, and is only CAROL's experience, granted, Al does most of the driving, but I am doing more and more, as we find that we don't arrive at our destination as tired when we share the driving load.
Carol