1. Grape spacing at 8ft is OK but your math may be wrong. You have 64ft (8x8) of grapes in a 50ft row.
2. Varies by spacing but I would go with two posts.
3. Yes.
4. Red raspberries, like Heritage, sucker freely and will continue to fill in all available empty space. If you are not going to put them in a raised bed, then put in a physical barrier to slow their spread into your blackberry area. You can use a few cinder blocks and dig down about 4-6â to set them. It wonâÂÂt fully prevent the red raspberry spread but it will keep it manageable.

There are a number of online resources with pictures, measurements, and advice for grape trellises. I would highly suggest reviewing those if you have not already.
You didnâÂÂt ask but IâÂÂm going to provide my opinion on your blackberry and raspberry selections (thatâÂÂs what we do in this forum).

- Triple Crown is great but you need 8ft between the plants.
- Black Satin is not so good. It will overlap your TC harvest in late summer and will likely get infested with SWD. The flavor is poor too. Try an earlier fruiting variety like Osage or Ouachita (3-4ft spacing) and you will have a longer period of blackberry production and avoid SWD on the earlier varieties.
- There are newer varieties of red raspberry that are superior to Heritage. Both Prelude and Caroline would be very good choices for red raspberries.

The number of grapevines should be 6, not 8. So it is 6x8 to 50'.

As for the varieties, this is only the first batch, this fall planting. I've had some of them for years, but got neglected and lost in the weeds. Some are from the same vendor where I purchased some fruit trees. But they do not have much new varieties.

I'll order all the grapevines and a couple of more berry plants this spring. Then I'll do some comparison and may use some for fresh eating and some for baking and drink etc. I may open another small area for experimenting. But 10 berry plants should be enough for personal use.

Black Satin is an excellent berry for cooking. Those and the Triple Crown will both be subject to SWD. Boysens are a bit earlier and may fare better. You will likely get sun damage on the south-facing TC berries; you can prune away more south-trending laterals once your total crop is sufficient for your needs.

The TC can be spaced at 5 feet, just do more pruning or overlap the laterals for higher production.

The berry row will be behind the grape row. So they will be somehow shaded by the grape vines.

I'm thinking of spacing the blackberries 5.5' and the raspberries 4.5'.

I'm thinking about pouring some concrete mix at the foot of the end posts instead of the anchoring support. This way, I can save some footage of the bed?