If you are hand planing, the row should be about 2 1/2" from edge.
You will have to extend the wood part of vise to edge of bench which you should do anyway.
I would not go drilling a lot of holes in your bench until you start using it.
I really appreciate all the ideas given here, it has made me rethink my whole plan. At this point I am thinking of getting rid of the end vises which were dictating where I put the holes. Or at the very least, putting a wooden jaw in the front end vise with a dog 2 1/2” from the front. I also need to look into the 96mm grid idea, but I am really hesitant to drill that many holes. I am still a ways off from drilling holes. Thanks everyone!!!
I really think your bench deserves a full width vice unless the screws would foul the base.
http://www.leevalley.com/en/wood/pag...=1,41637,45114
You could also use the Veritas double end-vice setup that has the chain to keep both rows "in sync".
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The most expensive tool is the one you buy "cheaply" and often...