It’s the proximity of the outer U-bolt nut nearest to the chassis rather than the springs that can cause a problem. If you do suspect that they are 4 seater springs then there is one check worth doing IMO….. Nothing to do with ride quality but more to do with care for the car.
It’s important that the U-bolt nuts/bolt ends are not able to make contact with the chassis as the suspension extends on bumpy road surfaces. My understanding is that if there is any contact there is a risk of developing a crack over time in the thin chassis section owing to the repeated hammering effect. It’s not something that you would necessarily notice when driving so something worth checking because if a crack were to develop it is almost impossible to repair owing to the flexure of the chassis. I think there is a bit somewhere on GoMog about it.
The check. Place a piece of paper under the nearest U-bolt nut to the chassis return on each side of the car. Jack up the car on the rear cross member and allow the axle to drop. Then check for contact between nut and chassis return by seeing if the paper is pinched or not. In fact there should be a few mm of clearance to be on the safe side.
The paper was well pinched in this picture of my car. The 4 seater springs were swiftly removed.
The spacer between axle and spring doesn’t effect the clearance between nut and chassis, their purpose is to just lower the car.
I’ve managed to get your longer stops in the post today as I’m going to be tied up during the day for the next week or so. Let me know how they go.