The crossrunner has a very upright riding position, so from that point of view it should be good for your back. There might be a problem with the footpegs, which are fairly high, although I believe they are lower on the 2013 models. It's a fairly heavy bike, not when riding but when manoeuvring and putting on the centre stand.
The only real test is for you to ride it and compare to other bikes, make sure it is a long test ride as a bike can feel fine for 30 minutes but when you spend several hours in the saddle it can show up areas that might be uncomfortable for you.
Hope you find a suitable bike and can stay in the saddle despite the back problems.