I put vines in at eight foot spacing and wish I had done ten or twelve foot. It would have been easier to manage.
* some varieties as Frontenac and concord are “vigorous “ it will take periodic summer trimming to keep them in control
* what size mower do you run? It bugs me to do up the row and then down leaving eight inches uncut
* how many thousand pounds of grapes do you want to deal with? Plant higher density if you want to optimize pounds yield. A correlation to this is what kind of press, tanks, filters, shed, do you own or plan to own? You have a tractor and sprayer and equipment building?
* 2.5 acres eventual is as big as some European vineyards. Do you want to eventually get a license? Is the plan to sell to a regional winery? ,, the big winery close to me said half an acre was big enough that they would buy my crop and small enough that a single individual could manage it.
* what is your topography? hills slope south? other as ponds? access roads to property and lanes to get equipment to the vines?
This sounds like a fun project
, , which I might have tried if twenty years younger when I retired.