No further progress on this, but I did find this video:
It's all speculative CGI, but it's an interesting concept. For instance it claims 15x thrust, where Jetoptera gets to that with an additional box wing. 10x from Coanda and one level of entrainment?
edit: On the subject of quadcoptera, I've been learning about the Prandtl wing and found a mention of a Prandtl propeller! It would be longer ...but quiet. All the noise comes from the tips.