Amin
Hall of Famer
I don't think anyone visiting these sites will easily find (or understand) those links to the other sites. I don't know what other issues you are balancing, just saying that if you want to spread traffic to the other sites, I'm not sure noobs who stumble on one will find the other sites.
Those buttons and links were always intended as a convenient way for members who participated on more than one site to get back and forth, not a way to advertise other sites to unaware noobs.