One of the prime reasons why a leaf spring's ride is not as supple as a coil spring's ride is because of the internal friction in a leaf spring. I believe that this is the reason why various OE's have used single leaf, leaf springs in passenger cars. The leaves rubbing against each other as the suspension tries to move causes a delay in suspension reaction that the riders in the vehicle feel as a slight harshness. That friction also results in the springs being somewhat self-damping. This is evident by looking at the Bilstein valve-stacks generically recommended for leaf sprung vs. coil sprung vehicles.
The commonly swapped into Mini's (& other vehicles) GM 63" long leaf springs have a good trick that can be copied. They have tip sliders at each leave's tip. Nothing new there, lots of springs do that. What they do that I've not seen done anywhere else is they have thin steel shim spacers between the leaves at the center bolt. These shims are long enough to extend beyond the U-Bolts, but not much longer than that. This results in the leaves only touching each other at the tips. There are air gaps everywhere else. Putting these springs under the rear of my Mini forced me to slightly stiffen the shock valving. That spring swap is one of the top 3 suspension mods that I've made to that truck and I am considering trying to fit a set under my 60 once the engine swap is complete.
I didn't know the 63" springs had spacers between the leaves. Sounds exactly like parabolic springs, but with a standard leaf shape. That's coming up on my list of mods for my truck.