A friend who I wont name (think he's a transport manager now!) was on an agency run down south with a nice big all electronic Scania, offgoing driver tells him how to disable the limiter (use gearlever like a playstation joystick, three left two forwards one back etc etc) and that because of the electronics the tacho will just show a steady 56... (just before the transition to all electronic tacho's, shows my age!)
"Bonus" thinks boy wonder, does so and gets a flying run in, back in good time, all happy until he pulls out the tacho to see it off the speed scale for most of the run. Queue white faced agency driver quickly thinking up excuses for a torn up tacho "oh it didn't record for some reason so I had to do a manual..."!
I can truthfully say I've never "pulled the fuse", imo the only person who wins is the boss, never the poor driver :-/ We all know about dodgy practices like the ones you mentioned, dipping the clutch on downhills etc though.
Funny you should mention the A9 in that context, last time I was in Inverness in a heavy a colleague in another one was doing 50+ when he spotted the mobile camera... not a happy time for him wondering if he'd been clocked and therefore would be unemployed soon (his company have a very strict points policy). Just not worth it.