Wow, congrats on your progress so far!
It's great that you are giving kettleworx a go. Is S&S a vlcd? If so it will be interesting to hear how you find energy levels for your workouts. Have you asked your gp if there's anything you need to look out for/avoid given your joint/back problems?
Because of them I would pay extra attention to form, sometimes kettleworx goes quite quickly and it's better to pause and do the reps in your own time rather than risk hurting yourself. If you find it a bit much at first you can do some core strengthening on your own to build up a bit of support and then try again, that's what I did (I have M.E. and when I started kettleworx had chronic lower back pain/sciatica issues - nothing like hypermobility to worry about though!).
Good luck, keep us posted as to how you're getting on! x