I have placed a 5mm spacer between my exhaust hanger and the frame. I still have the OEM exhaust. So this brings the exhaust a little closer to the swingarm. I measure now 285 mm.
So the Arrow will be about 2cm more narrow. That would be OK.
I live in Belgium. Approval is not very important here. But I often come to Germany. Will there be a problem with a exhaust that has approval for a 1190, but not for the 1290?
I think Arrow will have approval for this exhaust in the near future. I wrote them a mail, but they do not answer.