I missed the parallel bracing and had X bracing stuck in my head from looking at the back bracing on your blog. I've done a few archtops with parallel bracing without the transverse brace like on yours. It still looks plenty substantial enough to handle the downward pressure of the bridge and strings but hard to tell just from pictures. I used X bracing on most of my later archtops as I'm not much of a jazz player and like the milder highs and increased bass by using X bracing. An F5 style mando has been on my list for a while. If I played one more, I may have done one by now but do love the sound.

Darrel