Well Jason, we're just going by standard GTP OLR racing rules, slightly modified to suit our needs of course. The OLR stipulates, in basic form, that most hard track-edge surfaces, especially rumble strips, are considered track. We outline track boundaries in order to provide for the best racing possibly. For a track like Monza we like to use all the track that GT provided us with in order to keep the speeds up and have as much room as possible for our drivers to fight for position. In GT5, and in GT cars, it's much easier to use all of Monza's kerbing in order to produce easy, fast, and fair racing lines. But we're strict when it comes to the illegal use of extra run-off, and greencrete cutting.
But if you look at GT cars or F1 cars that run Monza you'll notice they use pretty much the same lines as we do (save for a few corners where the kerbing is actually higher in real life Monza than in GT5 and isn't traversable ).
Here's a good example:
PURE, the group that helps run the GT4 Cup with Aderrrm, has been organizing series since the launch of GT5 so you're in good company.
And the video of some practice laps of mine'll go up shortly, I had a couple good ones going but ended up messing them up at the last sector and the parabolica especially, then I had a big shunt, but meh, still happy.