I think 8 is the most 1080ti's you can run safely with a 2400 server psu. I use this pico:

https://www.ebay.com/itm/6pin-input-DC-12V-250W-24pin-Pico-ATX-Switch-PSU-Car-Auto-Mini-ITX-power-module/222612804598?hash=item33d4c1d3f6:g:tjoAAOSwaBhZkP~-