Hy , first of all i had the same problem, wel actualy similar ,i use 2 fog servers , one for windows XP (with an old fog ) and antoher for W10 (FOG 1.5.8), therfor i had to redirect the pxe boot for each host.
fix 1 : may sugest that u don’t instal the fog service in the “default” windows image at all…this way , after u deploy the image, u can asign each host to the desire FOG server when u setup the “SmartInstaller” with the fog service
fix 2 : i’v manage to change the FOG server that hosts respond to by editing the “settings.json” from “C:\Program Files (x86)\FOG” …the only problem with this is that i had to click the “reset encription data” from FOG Web manager, of that peculiar host ( and other host’s iv changed from 1 server to another)
In case u wonder why i use 2 fog and why i use windows xp…the company that i work in has around 1700 hosts and old software that work only on win xp