Welcome to the new and improved Proflex / K2 Tech Forum!
Correct me if I'm wrong, but the 857 bottom mount is different than the 855, yes? I believe the 855 has a cone shaped fitting that goes into the strut blades. Hmm...was it JuanPablo that made an adaptor for the 855?
Any issues of "bodging" with your setup? I checked out the thread of your install of this and it seemed rather inconclusive.