When plowing small powder, I am sure I have been above 5 mph. A foot of wet stuff is a different matter. With the plow raised, I keep it below 25 mph, but only for short distances between my properties. Otherwise it is easy enough to disconnect.
This plowing setup is modified from their design for a side by side. It was not originally designed for the power, mass, and ruggedness of the Roxor. Hence the warning to take it “slow” at 5mph per my discussions with their helpful tech.
This is not a heavy duty, for-hire rig. But it works great around my place and the neighbors. No issues in 4 years when used sensibly. But I could see it bending/twisting/breaking with rough use. Hitting a hidden obstacle above 5 mph might not be pretty.
Because only gravity holds the blade down, dragging snow out of a tight area in reverse is not really an option as the blade just rides up fyi. That is the biggest shortcoming, along with manual blade angle changes!