Bob,
you dont say if you have replacement standard springs, or the spyder rear suspension conversion. As I understand it, the spyder conversion uses adjustable spring platforms, and from wha I gather stiffer than standard springs.
I have a similar set up on my +2 and I’ve not long fitted new rear, small diameter springs.
The back of the car does sit a wee bitty high but there’s still an inch or so’s adjustment on the spring seats which I haven’t used yet as I’m waiting to see if the back end settles a bit. The car has only done a few hundred miles on the springs.
I have a total Spyder suspension front & rear. The springs supplied by Spyder were all too long, even with adjustable shocks.
I replaced them with specific rate/length springs from Demon Tweeks, and still had to make up 65mm spacers for the rears. My ride height is standard, i.e. lower wishbones horizontal with driver & passenger up.
At least wait till all your glass & seats etc are all in before faulting the ride height.
You do not say if you have the mk1 rear suspension or the current mk2?
I have the mk1 set up which was fitted in 1985. I contacted Spyder about the spring rates but they were not interested and said I would be better to buy a whole new mk2 set up at ?1200
I have renewed my broken springs with new ones from Demon Tweeks for ?50 the pair. I used 100 lb/in springs but at the moment they are grounded, I am about to adjust the shocks right out and try again. I will let you how I get on if you want??
I have Spyder Engineering springs and control arms with the OEM bearing carriers and spring perches. I will see what ride height I get with the completed car with weight in the seats. I was told I had add weight until the arms were below perpendicular then torque the attachment boltss/ bushings. This will “hold” the car at ride height compressing the springs.