> Kuda on the UK allowing higher loads, and therefore benefiting from extra wedge devices on the top of the cab.

Cab-top deflectors are extremely common on every truck where the cab is not tall enough to cover a standard trailer (which is common, usually only the highest end sleepers are that tall e.g. Scania's highline cab on the R and S, Volvo's globetrotter xl and xxl, ...)

For instance on this hero image from scania's site every truck but the very shortest and the very tallest have a deflector: https://www.scania.com//group/en/home/products-and-services/...

Obviously if you run higher than standard trailers, you need a custom deflector.