Tracking an airways doesn't use rudder at-all, regardless of crosswind component - that's just geometry.
Do conditions change things - a bit. But, you'll generally shoot for steady conditions, and I don't think that in the last 50 feet shear changes very much on a standard open grass + tarmac airfield.
The limit will either be the worst seen, or the point the test pilots decide it's become unviable (as I said, around CHR5.) And of course, anything based upon pilot opiinion is, to some extent, subjective - it can't not be.
G