No. I've had bad backs, 2 collapsed discs in the lower spine and excrutiating sciatica. Found it difficult to sit down anywhere and I used a 'back chair' with a tilted forward seat and pads for knees - so you were half kneeling and half sitting - with back vertical.
But when I was coming out of this issue, I found that the most comfortable place to be was on the ST1300. I could (and did) ride for hours.
Mind - getting feet down to the ground required a bit of forward planning, and I had walking poles in the top box for when I got off.
When the ST1300 first arrived, I sat on one. It was terrible - so much weight on my wrists. I was leant too far forwards. I stayed with my ST1100A for a few years. IT was four years later when I tried again and sat on one with a bar riser fitted. So I bought one brand new in 2007 - brand new ST1300A6, fitted a bar riser.
I suppose it depends where your back pain is. I can imagine that between the shoulders could be an issue, but I've never had it. First rides after winter, I get pains across my chest - which was worrying until I realised what it was. Sub-consciously gripping the bars too tight and wrestling the bike rather than riding with it. It only takes a couple of rides.