I know exactly the stabby pain right in the blades you describe - almost as if it were underneath the shoulder blade/s. I thought that the upright dirtbike style riding position of the strom was supposed to prevent such things, but no.....
Only when I swapped my stock handlebar for an aftermarket riser bar (the inexpensive steel $20 MSR one I chose is 2" taller), did my shoulder blade stabbings go away. Sure, I had to do a bit of creative cable/housing management due to the extra 2", but it was really a transformative modification. It's really the stock bar bend, combined with what is acutally a considerable reach to the bars on a strom
(it's a big bike!). Hard to say if it's only
the stock bar causing it, but by reducing my reach to the handlebar (I angled the new bar back a bit too), this took all the stress off trying to hold and stretch
my arms forward to grip the stock bar (you don't think you're doing this, but you are!). I believe on bikes like the strom, that it's much more forgiving on your back, if you have MORE bend in your arms - more than what you'd see on a typical sportbike, for sure.