I cant really see from the pic but I assume its clamped to the spring? That is how it is described in the nissan competition leaflet/book that was posted on here a while ago.

Do you think that 20mm will turn it into an oversteer pig? Seems awefully big...?

From what I can see, the sway bar will have little to no effect, it needs to be attched to the chassis somewhere.
It looks to be mounted too far back on the spring?
Let us know how it works.

I think being that close to the end of the spring it functionally IS attached to the chassis, no?

ordinarily a 20mm bar would be excessively large for the rear, but that setup will be less effective than if mounted to the chassis, so you might get away with it.

looks a bit close to the chassis rail too - have you checked for bind at full travel? if it happens while you're driving, you'd want to have lightning reflexes and excellent car control skills.

What car is the bar off?

L18 - clearance is fine. I know people say it a lot but the picture makes it look closer than it really is. Also that position only moves less than half the travel of the diff still alowing around 5-6 inches of travel.

If there are issues with it bottoming out it will actually mount to the underside of the spring by swapping sides with the brackets. The only reason it's where it is was because the bar fouls the diff housing when swung down that far. It could be resolved by spacing it off the diff housing further though.

I'm not claiming any brilliance with this design but I'm betting it won't be completely useless and I just worked with what I had.