I haven't. But the problem is the back of the bonnet is tyoically a low pressure area, so if you raise it or add a vent at the back air will come in there. Which from a generally getting fresh air blowing around the place perspective is a good thing, but it will negatively impact the amount of air coming through the radiator and intercooler. How much? Don't know.
Whilst that will probably reduce the engine bay temp a bit, and seem better to the non scientific approach of touching the rocker covers or plenum, whether it actually aids cooling the engine is questionable and could actually make it worse, as the radiator
And intercooler might not work as well.
End of the day its pretty easy to chuck some spacers on and see how you go. I would be inclined to tape some string around the area to see which way the air is flowing. Or streamers, they look heaps cool on cars.