AFP (ACL’s on) writes 755 privs on every file….

I know, I know, with ACL's on why should it matter? Well... Renderman completely ignores the ACLs when it renders, it only obey's POSIX. It renders a frame (as a jpeg or exr) and in-order to render the next frame it must open the previous frame. The problem is, since all the frames are written as 755, renderman can't open the frame file to write the next one. How can I change the default write permissions for dirs on our Xserve with ACLs on? Any ideas?? (chmod 2777 did NOT work.) Puleeeeeeze help! Thanks!!