Hi Neil, It definitely appears that Reikan is working hard towards releasing a Mac version ASAP as only a few days ago the leading developer indicated that was their highest priority.
With regards to targets: Whether-or-not the target is printed on heavyweight paper doesn't seem of great importance. I believe that it is more important to mount the print on something fairly rigid. In my own case, I have my targets mounted on 1/2inch foamcore. While I cannot rate the importance, it makes a great deal of sense to print the target(s) on a MATTE surface paper, with a fairly high resolution INKJET printer - ideally using a matte black ink.
FoCal seems to be pretty fussy about both the camera and the target being held as rigidly as possible. This is particularly challenging for users of Nikon camera bodies as the "operator" has to manually enter values for the FT adjustment settings after they have been requested on-screen by the application. It is very important that doing so does not move the camera! For Nikon bodies, FoCal is able to READ the current FT setting, but cannot SET it. This is due to Nikon not publishing an API (Application Programming Interface) for that function. Apparently Canon does - so more of FoCal's tests can be fully automated with Canon hardware than for Nikon.