Sure, you can grow a grapevine in a pot and train the top to any form you want. I've got one growing in a 15 gal pot. The top on mine is about 3ft wide by 5ft tall. But the top can be trained to follow any form you want. Just run a cane up inside the metal circles the first yr.

I'm not sure if Concord is fruitful on short spurs or if you need long canes. But either way you can figure out how to get the shape you want and still get fruit.

If it is fruitful on short canes, then you can have a permanent trunk and head, perhaps in the shape of a T. Short fruiting spurs 3-4 buds long will be left on the head of the T each time you dormant prune. Fruiting canes will sprout from these 3-4 bud fruiting spurs each yr to bear fruit. The new canes can be trained to run up the inside or outside the circles.

If you need long canes to get good fruiting, then each yr you need to run one or two new canes up inside or outside your circles. These will fruit the next yr. So each yr you would have last yrs cane producing fruit and a new cane or two to produce fruit the next yr.

There will be shoots wanting to run horizontally any way you do it. Just prune these back every couple wks or as needed. There will also be extra shoots coming from the premanent parts of the vine or even from new growth. Again cut out anything out of place. The only caveat is you have to know what will be next yrs fruiting wood and not cut that out.

The thing about a grape is, if you don't like it's current form, you can always change it next time you prune. Try it and you will soon come up with a form that suits you and fruits every year.

The Fruitnut