If I may, I've found fox to be MUCH more "fragile" than coyotes. Combinations that work beautifully on coyotes, have blown up fox badly for me.
Out to ~ 200 yards, I wouldn't hesitate to use my K-Hornet with 40 gr V-Max. The 35's would probably be better on fox, but I wouldn't bet, re: coyotes.
Just my slightly experienced views.
