I don't like your chances getting an informed first hand answer to that.... a b owner and a pure (or classic) owner that had fitted a Wilbers rear shock to their pure/classic at some stage...... and regularly reads and comments in this forum!
Fwiw... with my "pure".... with stock shock.... with preload set.... tyre air pressures set etc.... I have/had no concerns with high speed corners..... however.... high speed with sharpish mid corner bumps was less then ideal.... but that is forks as well etc.... (I find my pure confidence inspiring doing say 70mph around a signed 50mph corner as an example... but I would be actively riding on a road I know.. not zoned out cruising).
And... now with the Wilbers rear shock.... I will say.... 3.5" of travel will have it's limitations no matter what. FWIW..... i have a high speed open road railway crossing just outside of my town..... with a sharp bend each side of it.... that I use as a part of my bike suspension set up test.... on my r nine t scrambler with new aftermarket suspension I can stay seated at 50mph going over it..... R 18 is 30mph with the Wilbers.... so everything is relative. I did try 50ish.... big mistake.