Road speed up the grade is irrelevant. I wouldn't run fast even where I could. Too many vehicles are slow. The increasing stupidity of car drivers has accelerated in rate. And a combined rig can't get out of its own way. (Read that again).
When the Interstates were being built I thought then (and now) that it's wrong to have a high upper speed limit on ascent and descent.
The ONLY thing that matters is control down the hill. Those with trailer anti-lock disc brakes raise their hands.
(Yeah, I thought so).
Little boys