My wife (gawd bless her) suffers from back pain; the ride in my 1989 +4 2 seater is very hard; I love it as it corners on rails (as should be) but the old story of telling the difference between fag ends being filter tipped or plain when driven over is very true. My previous 1961 +4 had sprung upholstered bench seat back rest and float on air cushions on plywood base. I never had problems with this set up.
I am tempted to investigate new bucket seats with more upholstery/strings. Before I do, any suggestions from fellow morgan'ers/suffers would be greatly appreciated. (and no - I don't want to change wife or car!!)
I would say it's more of a lumbar support issue and the rake to the back of the seat.
We over came this in stages.
Michele has a Foot plate so here legs are not flat outstretched which helped no end, we then lifted the nose of the seat to tilt her back into the seat, and lastly a inflatable lumbar support.
But on early cars the Lumbar Support needs to be fitted by a pro as they don't slip in as per the modern seats we have in the later Mogs.
Bucket seats are fixed back so much thought would be needed as to the rake required.
Hope this helps
