Either of them should be fine. One way I think might be easier is to put the trellis right in the middle of the two squares so the plant can just grow straight up instead of having to find it's way over to the trellis.

I had that thought as well.

I guess my underlying questions is: what is the rationale for this planting guidance? (I'll probably wind up asking Mel, but I wanted other's experience as well).

If the reason Mel suggests planting 1 plant per 2 sq ft is 1) these plants need a lot of root space, nutrition, etc. OR 2) the vines/leaves take up so much space that two feet are needed for above ground spread (especially on the trellis).

If the answer is #1, then the orientation of the plant to the trellis is not important - the plant roots will grow where they will; however, if the answer is #2, then a possible solution is to make the trellis wider than the SFG to give the plants extra trellis space and still get in four vertical plants in 4 sq ft.

Like you said, probably doesn't even matter ;->

Thanks again