I own a vitpilen 401 wich is pretty much the same as a rc 390. Searching on the vitpilen forums I found this. I think this would solve your problem. I was wondering on doing the R1 shock instead of the R6 but I think that the R1 shock doesn't fit neither upside down.
Tell me if this fixes your...
Hi Chuz,
Have you solved this problem? I want to change my shock but I'm worried about hitting the exhaust. I'm actually running the arrow de-cat pipe.