I'm currently running:
150/90-15
25.63" in diameter.
I've got about 3/4" clearance.
So I'd say your tyre would go on my bike, perhaps 1/2" of clearance? Getting pretty tight. Like others say the swingarms probably vary a bit - I don't think they're laser cut.

At a guess 1/4" clearance difference between bikes?
I am going to go 17" at the back eventually as I want to get away from the cruiser look and am happy enough with 17" to not bollocks around cutting the swing arm. When current set of tyres are done I'm gonna get the back wheel respoked 17" and run 120/90-17 which are 25.5" so will fit fine.
tyres will look like this:

Pretty nice for a scrambler/flat tracker type. Not pure cafe but a bit different is good in my book.
My current tyres may last a while though the pace my build is taking...
Where you at? I see you on dotheton as well.