I have left mine to grow over, around and through a chain link fence and prune in the spring-
My sister farther north likes to prune in the fall- She leaves the main trunk with 4 or 5 leaders trained against a pole barn wall. She prunes back most all new vines as the growing season progresses and the plants energy goes into growing more and larger grapes than vines. Something like a tall MN version of CA wine grapes.
We 3 may have very different plants though- I know that ours are hardy without any special care. Maybe yours is too- I cant say. Maybe yours just needed extra protection through it's first winter while its roots became established. Although- I can see how a MN rose tip could help a tender grape.
As a general rule, Concords flower and fruit off of old woody vine- I would suggest you leave a main trunk- and maybe a leader or two off of the trunk this year- what is the worst that could happen? Your root mass made it through last year just fine- and that is where the growth starts....
I hope this helps-
Julie