Have you taken any heat measurements with multiple in the same hub? The heat spreaders look like they may help, but the old ones got insanely hot and with a 10X speed increase I wonder how hot these are in a group.
I can take some measurements for you tomorrow.
I have a 10 port hub with 5 NF6's running slightly overclocked. There is a USB fan on them and the surface temperature of the miners is 41C. Without the fan they would be about 72C-82C.
Because of their deepth you would not be able to fit more than 5 on a standard 10 port hub. If your hub ports are tightly packed you may not even fit 5.
I have 49 port hub on which I have run a maximum of 18 NF6's. The limitation there was more my PC than the hub itself.