Well SAP's have been said to do better as a group, while Dwarf's go okay togeher with a ratio of 3:1 (with 2 females to every male) and as far as F8's go, it really comes to individual personality, although they are known to be friendlier... but as with ANY puffer, it comes down to the puffers individual personality as to weather or not they will accept tank mates...
I think PufferPunks Fahaka is a great example... you just never know when they might decide to turn...
Just my 0.2cents