I built this trellis, roughly following your plan, and it's still early in the season so we'll have to see how it works out (been cool and rainy here -- not the best tomato weather). I did a few things differently, though -- first, I canted the ends in a bit, by making the top chord shorter than the bottom. This gave me better stability, I think, and less likelihood to sway to either end. Second, I put strips of lattice up across the end struts in order to use them as additional trellis space in my cramped community garden. I think this adds potential to your design in any situation. Finally, I used these strips to tie horizontal strings (woven on either side of the vertical strings) to add more plant support.

I'll let you know how it works out. Thanks for the idea. Passersby sure seem to like it.

Pete
Boston, MA