AS far as vinifying goes, I can't give much advice but growing Frontenac is a different story. I usually get 3 cluster shoots. In their 5th year I pruned them down to 2 cluster shoots with 7 or 8, 2 bud spurs on 2 arms. It was relatively disease-free, but I could see the over-cropping effect the next year. 75% bud kill from winter damage after a winter low of -3 or 4. I made the mistake of counting on that bolstered winter hardiness to save the vine in case I over-cropped. Its year 7 and it recovered nicely. I pruned the same but only 1 cluster per shoot. As rule of thumb, you should cluster thin outer to inner and you should thin it pre-bloom. If you're getting 4 clusters per shoot in an area that gets relatively less light intensity ( I say that because light intensity is a big factor on next years productivity), you have a healthier site. 2 clusters might be fine but don't be surprised if you get winter damage. Over-cropping can be detrimental to vine health and fruit quality. The ripening fruit becomes a sink for nutrients and can spread the vine too thin. Some vines are hard to over-crop. Frontenac is not such a vine. What I do know about making wine with it is this- let the fruit hang as long as possible and get that acid down. It also helps dissipate the herbaceous flavors associated with fronenac.. IIRC, Peter Hemstad, the breeder from U of MN who created that vine among others, said that it is best blended with Marquette
