I have two concord grapes that growing on sides of small arbor. Last year I cut them to the ground to start a new shape. I want it to be a very low trunk and one arm for each grape. After it came up it grew very vigorously, and even produced flowers in the mid of July. This spring I left one 5’ long arm going strait up and one 2 buds stick to grow replacement arm for next year. I hoped that fruiting wood will appear from all buds along the arm. However, it is not the case. For one grape only 5 top buds woke up, and for the second - just one very top one. They are not new bushes, so root systems are pretty big and strong. They basically got back to the shape I tried to correct when I cut them - very long empty trunk and no space on the top for fruiting wood. Is it because the arm goes strait up and “decides” to be a trunk? The replacement stick produced two shoots, so I can use one as next year arm and one as next year replacement, but I don’t want to get in same situation again.
Not a big grape person, so that’s my advise with a grain of salt.
At times one can nick above a non-growing bud to encourage growth.
However, I don’t know if this will solve your problem. My own grape (just one, yes) seems to fruit on horizontal wood, vertical wood only grows but doesn’t out on spring growth. I think I’d nick above buds on the one with only growth at the end.
Then again, perhaps someone with more experience will chime in…
And perhaps we will both get grapes this year.
Scott
With this structure it is almost impossible to make horizontal wood. I didn’t know better when I planted it on the arbor. From other point the arbor itself is must have - it is only structure that prevents snow to be pushed in my yard along with tons of dirt from unpaved road. For a few yeas I am thinking of removing these grapes and put in something else like climbing rose, but every year I decide, OK, I will try one more time 
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The first push is toward the top as would be expected. Water and fertilize as needed and I’m pretty sure some of the other nodes will start growing. You can also tip the higher buds out past the fruit to help push out the lower ones. Once you get some lower growth it will be easier to achieve what you want.
Thanks!
Zig zag the growth up the trellis. A grapes tendency in the wild is grow straight up through a tree and make the grapes in the canopy of the tree. It eventually kills the tree in most cases. Vertical growth does not make grapes whereas horizontal growth does makes grapes by design. If you zig zag the growth on the trellis you will get some horizontal growth that way. Grapes do not like excessive nutrients so fertilize enough for growth but with grapes that’s a fraction of what most things get fertilized.
This is a great idea. I will try it with new shoot that will be next year arm.