I've been thinking, and just thought I'd pass it along.

I, also, have Spondylosis, Spondolethesis, (like you - SIC) and found what works for me. Like you, my only permanent fix is a permanent repair of the vertabrae in question. My bonecrusher recommends that I put it off as long as is humanly possible, because of the lightyear strides that are being made in back surgery every day. He strongly recommends that we wait, and get the best result possible, on that given day.

I came from a road bike, of many years, and started looking for something that would be more comfortable to to ride. I RODE MANY, and settled on a Hybrid (heresey, I know).....

More specifically, a front suspended, performance Hybrid, with fatter tires. And, even a little oversized.

Technically, I should be riding a 58, but found the stretched out riding position of a 61 was light years ahead of the other sizes for comfort. Still lets me sit "basically' upright, but more stretched out.

My Crosstrail (08) came with 45 tires as OEM.

Tires, 45s are really comfy, but I found that a 40 on the rear is just as nice. 35s on the back, are too harsh, but work very nicely on the front for quickening up, and making steering more precise. I'm running this mix, in Schwalbe Marathon Supremes, and run them at 85 PSI. Soooooo, I settled on 35 front, and 40 rear.

Between the tires, and the front suspension (cranked all the way to max) and I even lock it out when on smoother pavement, the ride is better. So much so, that the shocks which used to cause really bad problems, are a non issue.

It's not really hard to get smooth enuf pedalling action, to, basically, keep front pogoing to a bare minimum.

I no longer have the back pain, leg numbness, foot tingling, and foot fires, I used to get when riding. I can now ride, MUCH BETTER than I can walk. When I mention foot fires, it's thast my feet, frequently, feel that they are on fire - literally. (Just a mixed up nerve sensation, I know.)

Food for thought!