I have not found a rule that says you cannot combine Half races e.g. (half-elf or half orc) with another race. For example half-elf and dwarf, or half-orc and gnome. The result would be, as far as CR is concerned, would be 2/3 CR, which is 1/3 away from having some sort of racial hit die. Another combination could be half-elf and aasimar, creating a CR of 5/6. Is this at all possible for PFS play?
Any clarification would be helpful.