I don't think there is enough room using the existing mounts.
I was looking very seriously into this before I changed to the Roadster with SSL 5 Link Suspension.
The coil spring would not need to be very highly rated and with adjustable spring seats on the coil overs it would give a way of setting the ride height and compensate for side to side sag.
I think it is do-able using separate mountings but it would take some development.
Of course you could leave the dampers as they are and setup separate mounts just for the soil springs.
Maybe Rog could adapt his bump stops.
