You might want to consider cluster thinning when they are blooming to get bigger grapes. If the clusters are too close, then you'll only get tiny grapes. This is from an extension article:
"Berry size compensation is of concern only when the berries are in phase I of development, during the first 3-4 weeks following fruit set. It is during this stage that cell division occurs in the berry, and removal of competing clusters may change the
carbon partitioning to allow for greater berry size. This is not the case if thinning occurs in phase II (lag) or phase III (ripening) of berry development.
"This equates to 16-18 leaves to support a single grape cluster. Remember, this is a general metric and more leaf area may be required in cool climates."
16-18 leaves might be approx. 12" or so, depending on the variety.
An important distinction: Permaculture is not the same kind of gardening as organic gardening.
Mediterranean climate hugel trenches, fabuluous clay soil high in nutrients, self-watering containers with hugel layers, keyhole composting with low hugel raised beds, thick Back to Eden Wood chips mulch (distinguished from Bark chips), using as many native plants as possible....all drought tolerant.