You get a 1.5L capacity increase actually... With a decently sized oil cooler, you could be looking at an extra 1-1.5L capacity, giving you 7.5-8L oil volume all up. Enough for most cars I'm sure you'll agree.
It does sit lower than the standard sump, but not by that much. I think the whole clearance thing has been blown WAY out of proportion. Most people harping on about the clearance issues are just regurgitating what they've heard on the internet or from other people verbatim, without actually having any experience with the extension kit itself.
Yes, it DOES lower the sump floor, but on a sensible ride height (100mm legal minimum height) GTR, it will NOT prove to be a problem on public roads. With it being close to the axle and hence the wheels, speed humps will not affect the sump. The only possible problems I can envisage are:
1. extra huge potholes and tilt the car at an extreme angle and cause it to bottom out halfway (not exactly common)
2. on the racetrack, if you undershoot the apex and straddle the ripple strips. That could hit the sump.... then again, that would hit ANY sump extension, Performance Metalcraft or Trust..
shoey: here's a link to the GReddy website, you can babelfish to translate it
http://www.trust-power.com/02greddy/oil_pa...pgrade_kit.html