It's amazing. Indeed, the 170 looks not that narrow at all. I would probably not even say that this is not a stock-size tire.
Is the 0.5 inch inner clearance an issue? It sounds like is getting close, but I guess it is a fixed distance so unless you get a stone or something hard in there, you should be fine, right?
'07 Vulcan 900 Custom, Candy Fire Red
'05 Suzuki DR-Z 400s