Thanks to everyone for their responses above regarding the use of plywood in frames. My contention was that it wasn't safe to simply say that the use of plywood is a negative, as my research indicated it can in fact be a positive. I think the take home message is that craftsmanship is obviously the most important factor in play. Whether that craftsman's choice of material speaks about their work is another debate entirely.
In any event, I've heard back from the folks at LeatherGroups in response to my questions about the suspension and request for frame construction photos. As it turns out, my assumption on the 8-way hand tied upgrade being drop-in was incorrect, this is done the traditional way -- frame attached and each point tied, no looping shortcuts.
Following are frame pictures. As it turns out, LG indicates that furniture plywood is used only on the arms for shaping. I'd welcome opinions on the construction shown. It looks quality to me, but I'm not educated on these matters. I've compared it to other frame construction pictures I've found at it looks comparable. My confidence is building.
If not linked elsewhere in the thread, this is the sofa in it's finished form:
https://www.leathergroups.com/cart/c...ofa-p-452.html