Thanks.
That's reassuring. The two stage retention system inspires more confidence than either stage on its own.
It's hard enough to get a decent range of DBEs to choose from in standard scale length and even more difficult to get a set of five. So far, I've not needed to put a clamping mod on either of my paddle basses but lots of folk do. I'd favour your clamping arrangement over one grub screw per string if it came to.
PS: It's all come together well. Although unfinished, it looks nicely proportioned