Got back to work on this. Have it bending to about 6" at 30#, tweaking the bends, about 2" to go before I'll string it...when I noticed that there's a spot where some of the fibers have popped loose on the opposite limb, not the same spot as the previous failure. Man.
I think what I'm learning here is that hide glue doesn't adhere all that well to dogbane, compared to sinew. It takes a ton of glue, and wrapping with string or ace bandage, to make sure it won't come loose. Or just use diluted TB3, but I really want to keep it as primitive as possible. (I used TB3 on the tip repair, so maybe it doesn't matter)
So. I guess I'll reglue this section, wrap it, wait another couple weeks, and get back to work on it. In the meantime, I have some nice, reflexed juniper pieces and a bunch of sinew lying around...