A suggestion for your Trucker friend: When decending a steep grade, shift one gear LOWER than the gear used to ascend the grade, and do this just before cresting the hill. This action along, with proper application of the manual brakes, should help the driver decend the grade safely and within legal speed limits.
Listen to Bricker. Get a lawyer from Virginia (I’d choose one with offices in the county where the ticket is written) and see if that lawyer can work out a deal.
In one place I lived a few years back, doing this would be almost guaranteed to turn your ticket into an “Improper Equipment” ticket. The fine stayed the same, but you’d get no points.
It’s a bit late, but here in the U.K. there’ve been a few cases successfully contested when the vehicle was ‘measured’ doing more than the maximum speed listed by the manufacturer.