I have some of those frost-hardy kiwis, three years old (one male, two
female). They have intertwined themselves in the back chain link
fence, and I'd like to train them over a (yet-to-be-built) pergola
instead.

When should I prune the vines, how aggressive should I be? I suspect
that they ought to be no more than a year from starting to set
buds/fruit, so I don't want to thwart my efforts at getting another
"snack bush" for the kids.

Thanks,
Mark