I gave a program to one of my weaving guilds about taking a four shaft overshot motif and weaving it on eight shafts. So thought I would share with you what I told them.
The idea is to have the four shaft motifs threaded on two independent sets of shafts, so the same pattern can be woven side by side. Now I didn't dream that up, I saw an article in the Summer 1997 Weaver's Magazine by Barbara Koch: Two For One. I did weave her draft.
Her idea was to weave the designs side by side in different colors as show above. That way you look at it and wonder how you could have woven the color on the diagonal. After all, you throw the shuttle across the warp not on a diagonal. By using an eight shaft loom she used shafts 1-4 for one motif, and 5-8 for the other. (The only drawback is you need 12 treadles.)
As you can see here, the same 'motif' is on the bottom for shafts and the back four shafts. Now, see her tie up. I decided to see what would happen if I wove the bottom four shafts in Star fashion and the top four shafts in Rose fashion. Now look at the same threading with a different tie up.
So now, I will treadle each in traditional overshot, but I will need to step on two treadles at the same time. One will hold the pattern for one set and tabby from the other. Then the next pick with the the other pattern and the other tabby. So it a color and weave effect too. Her is the Weaver Rose motif: Remembrance I did this way.
I now have the purple and gold colors running on the diagonal and also a different looking motif running on the diagonal. (and sorry, but I took a photo of the back side so you don't see my diagonal line through the star motif)
Thinking my self very clever to tweak the tie up for this neat effect, I was reminded that any weaving we might do has been done before. While researching another overshot question, I found on page 311 of the book: Pattern Techniques for Handweavers by Doramay Keasby, the explanation of this very trick. But I did enjoy the chase to figure this out. (If you can find that book or magazine article, maybe you will try this too.)