One of the things people ask when they see hybrid vines is what kind of training system are we using. We actually use a few different types depending on the vine and other variables including the growing style (uprights or sprawling) and the clusters size (production per shoot). So much depends on the growing style of the vine and the shoots per foot that we need to have in order to have a decent crop load.
For instance the L'Acadie Blanc, Ravat 34 and Evangeline all have good sized clusters varrying in size from 120 to 200 grams. So if we take L'Acadie blanc for instance, in order to get about 1-1.5lbs per foot of trellis space you only need 5-6 shoots per trellis foot at 1 cluster per shoot. The L'Acadie grows straight up like an arrow and is great for positioning the shoots in the wires. So because we only need 5-6 shoot per foot and they grow upright then we use a verticle shoot training system. Same for the Ravat 34.
On the other hand Leon Millot produces very small clusters of approximately 45-50 grams on average (sometimes 60 grams). Most shoots have 2 clusters so you get about 100 grams per shoot. This means you need 6-7 shoots per trellis foot to get 1.5 lbs per foot. But if you leave only 6 shoots per foot some of the shoots will grow at least 6 -7 feet long so clearly the vine could support the growth of more shoots. As such we crop at about 8 shoots per trellis foot and the growth is quite balanced at 24-26 shoots per meter. The diffference now is that at this density the shoots can become too dense (leaves from one shoot end up shading the leaves from another shoot) so we need to split them up and as such we use a 4 are kniffen style. But we do this with canes not cordons.
Our 4 arm kniffen style usally has 4-6 canes in total per vine with 2 lower canes wrapped to a 2 foot wire and 2-4 upper canes wrapped to a 3.5 foot wire and vines are spaced at 5 feet in the row. Ideally this means each vine has about 40 buds each (8 per foot over 5 feet) producing 100grams of grapes (2 x 50 gram clusters per bud). So production of approximately 4000 grams over 5 feet. So thats 800 grams (1.7 lbs) per trellis foot. We target 1.5 lbs per trellis foot for Leon Millot and this cropping level seems to meet that as sometime you only get 1 cluster per shoot and that brings the per shoot average down. Other vines could crop higher like Triompe D'Alsace, it could have 10-12 buds per foot but would be way to dense on a single canopy - this many buds per foot would have to be configured on some type of divided canopy like a geneva double curtain or lyre trellis style.
The the other factor with this density is that if you position all the shoot upward then they will still crowd each other so with the 4 arm kniffen they are also allowed to spread out into the area between the rows. Leon Millot (and most hybrids) vines don't grow staright up also so this fits well with their growing habit and even at 8 shoots per foot you will still get crazy long canes so we are always walking the rows and pinching back the shoots when they get up to 15 leaves in length.
One thing to note is that there are lots of documents that will tell you about pruning styles and how many buds per foot to have for certain varieites but less is known for hybrids. So use these as more like suggestions rather than guidelines especially as you are starting out but understand that you need to figure out whats best for the variety you have in the soil and climate conditions you have and in relation to ripening the fruit within the season you have. You need to grow the vines with different bud counts and training systems over a few years to figure out whats right for your location.
For a few years we experimented with different styles and bud counts in the same row and after two years quickly figured out whats best. Having said that, we changed things in the past 2 years with irrigation and fertilizer and now that has changed the growth of the vines (more vigor) and as such we have been working on modifying the bud count and the training system as well.