Simon my car pretty much uses the specs right out of 1200 competition manual.

I gravitate towards soft spring larger bars, I pound over the curbs so the softer springs help. I'm running 225-250 fronts, the rear springs should be 160lb mark. I say should because stock rear is 109 the 1200 suspension manual says use Nismo spring set and remove 3rd / short leaf which is 10% stiffer than stock but 25% softer than Nismo 3 leaf set up. I have the all 3 leafs so that should be 160lb spring.I run a 22mm front bar and 16mm rear bar (both Addco brand) The manual specs 25mm front 22 rear which seem a bit large to me.

The track width on my car is much wider than stock, I'm running the 510 wagon / roadster H190 (1350mm ?) the front track is 1365mm. I'm running 25mm roll center spacers under the 280zx struts. The 280ZX control arms are using the standard pick up points but they've been lengthened 19mm.

Alignment of the top of my head is -1.3 camber (Hoosier street TD bias ply spec no more than -1.5) 2 mm toe in and 4.5 degrees of caster. Ride as measured from the body join below the sill is 125mm front,( I could lower but risk the control arms traveling past horizontal and reducing the camber) the rear is a at 140mm. I can't lower the rear without having to modify the floor otherwise the H190 diff will small the sheet metal.

My car has what I'd call moderate oversteer; most folks would so a lot of oversteer but like most guys who started on motorcycles first I tend to like a car on the loose side. My local track is mostly low to medium speed corners it's an issue. The other factor is the car has got all of 105-110 whp, so being gutless as it is I'm pretty much floored from mid corner to exit in any corner over 60mph. If it had any real power I'd change the set up.

OK back to your car; the spring rates aren't that alarming after I thought about it, 2100 pound Spec Miata uses 750 front 450 rear springs. If you can snag a test day I would try go back tosofter springs combined with larger front bar in combination with small rear bar. Finally on the front springs if the car will take a set on low speed corner entry than I wouldn't worry about it. It one of those things you have test.

As for the roll centers I do seem remember that the rear should be slightly higher than the front otherwise the car tends toward oversteer.

I may have misread the post but how are you getting rear toe and camber? Is that a style,of axle that similar to what V8 super cars have?

One question I have is the car turning faster lap times with the new set up? If it is then I would work on the balance. As previously stated I'd adjust the rear, be if softer spring rate or roll center. If the car was slower I'd go back to the baseline. With it being Alan's first drive in the car I realize it maybe a moot point as far as lap times go. One thing I always go back to is the did the problem occur before I made changes. I also try not to make any changes before any events that I haven't had a chance to run at a track day. I don't like making anything more than minor adjustments on race weekends, my attitude is one of if you have work on the car more than 10-15 minutes to make a change you're not adjusting the car you're fixing it. I try to keep it to damper adjustments, sway bar adjustments and tire pressures.

The big thing is you are always chipping away at it, people don't realize how much that contributes to being a top notch car.

(Note I edited the ride height spec before I installed the H190 the car was 110mm front 120mm rear)