This is what I managed to get from the music shop. 8 for now and I'll get 6 more when the order comes in.

One swing on the wall. I measured the inside width of the wall and divided that by 5 to get the space for each guitar. Then I divided the width of a space in half to get the mounting points for each individual swing. As for height, I just eyeballed the first one and held it in place with a guitar in the hook and marked it. From that one swing I used a level extended to the next mark, slapped a swing on, and traced it. And so on... Repeated for the top row.

Bottom row complete!

Started top row. Crap ran out of swings, now we wait... 2 more swings will fill out that rather bare area in the top-right. The plan is to use 4 to stagger an in-between row to get an overall more pleasing look, though rather more tightly spaced than I'd prefer. It'll work, it'll work...