1) With the lifesize converter, this lens becomes an effective 70mm macro lens. I feel it is interesting to note that since the 100 USM macro is an
internal-focus design, its focal length reduces to an effective 70mm when extended to 1:1 -- this is because IF lenses shorten focal length to focus closer rather than move the entire lens group forward (as in the pre-USM 100 Macro).
2) I found that if I mounted my EF 12 extension tube on the front of my EF 1.4x II converter, I could then mount the assembly on this little macro and get to nearly 1:1 magnification (Probably this is a very similar optical arrangement to the life-size converter Canon offers for this lens).