ahhh rental driveways are always the best... Iv lost part of my 4mo lip already since moving to melb just from my driveway.
If your bumper is 100mm clear the underside of your car is prob hanging down a bit? My front lip looks a decent height, but as simon said, all the frame and parts under the car sit so much lower.
Bags would be nice. Maybe 1 day :p
bags can be anywhere from like $2k for the most simple of setups (im sure you could do it cheaper again) but ill be wanting the works so it can be engineered later down the track, which is like $4.8k+ for decent gear