Hi again Smiffy, I think the biggest problem I would be concerned with is your disc prolapse
Hopefully it is in your lumbar spine and not your neck because they require different approaches to healing and how you engage in surfing!
Just so you know where I'm coming from in my advice, I'm 63 and have been surfing since I was nine gone from long balsa logs down through short and back to long . Currently on 9ft boards and my shorts are 8fts. My healing advice will be based on thirty years working as a Chiropractor ( I'm retired)
Long boards and roof racks no problem I do six hour drives at motorway speeds with two longboards on top, only difference is an increase in fuel consumption! I've found poorly fitted roof racks get wind wafted when a semitrailer hurtles past at high speed especially going in the opposite direction. So my racks are well fitted and the boards tied down with ratchet straps.
With your disc problem and reading between the lines I suspect you are talking about lumbar disc , a sideways twisting wind wrench would be problematic to the injured area.
OH and BTW there is no problem in asking or even going against long standing stuff we are each unique in what we are and how we intend to go about doing what we do!
My advice knowing a few more details covers a few things.
For your back; have the diagnosis check and see about how you are progressing in rehabilitation.
Many of my patients have had prolapsed discs and and were a similar age to you after the initial problem and some time they were able to take up surfing again after physiotherapy.
Pilates is an exercise program that can strengthen deep abdominal muscles that support the spine which can then be almost problem free.
Gentle swimming and learning all sorts of gentle stretches will help, I don't advocate running or jogging, but long walks are good!A rider here; you need to talk this over fully with your health provider!
What it does mean is that prolonged surfs are not the go as the act of popping up also puts some strain on the low back over the time of the surf.
If the prolapse was in the neck , then the posture of looking while you are paddling is an issue.
If you want talk a little more about this please do so, as there are lots of others with this problem.
On boards see if you can get a few trial rides on boards between a longboard and a carpet, look at 7S boards and and assorted fun boards in the 8ft range and try a carpet too.
It might take a little time but use the looking time to get fitter, and the board will find itself.
I would be concerned if you hit the surf ,on whatever your new board turns out to be, without doing something towards a fit and protected back
I've taken up troll hunting just for fun, instead of a rifle I'll just use a pun!