We use RAFM minis with Artizan, Rattrap, West Wind, Pulp Figures, and even the old Grenadier Call of Cthulhu models. Aside from the "chunkiness" of the old Grenadiers and the occasional oddball figure, I'm not aware of any appreciable size difference. (And although not obsessive, I am a bit of a scale fascist...)
The Lurker force in the battle report
here (scroll down a few pics) includes a mix of West Wind, Pulp Figures, and RAFM minis.