Yep, I agree with the posters above - pick a good spot, and saw the ends of the feet off!

I saved about an inch or two past the heel to get SOME sort of support in place. Fortunately, if your costume has boots, they will often support themselves pretty well, if the costume isn't too topheavy.
For hands, I plan to use wooden blocks for the palms, and wire wrapped in foam for the fingers and thumbs. i will bolt on the hardware from the removable mannequin had so that the new one can be mounted in its place. Make sense?
-Raj