On the surface this seems like a ridiculous question, but: has anyone
cast a 5-weight Sage Z-Axis in the 9' and 8'6" size against one
another? And if so, is there a significant difference between the
two?

I'm trying to pick up a 8'6" used. But I'm only going to get the
chance to test cast a 9'. I know from personal experience that in
some product lines - like the Winston BIIx for example - the two
length rods actually cast with a not-insignificant different feel, for
some reason.

So - anyone ever compared the two side by side?