i figured out the measurements and made one of these a few months back....i think i saved them.....here ya go:
the bottom base is a circle 5.5" and then you sew on a piece 17.25x 1.5"
then use a 5" circle for the top of the base, with a 2" circle removed from the center and a the side cut (like a "C")
then the stacker was 7" high by 5.5" sloped with a 1.5" circle at the top.
it seems like i had to make some adjustments (i think i remember the stacker piece needed trimmed, that 5.5" was a bit too wide, but you can tell as you make it and just trim as you go).... and i sloped the stacker piece a good bit, but it worked out well. i just figured out the donuts, too....but i recently saw this, which might help: http://www.michaelmillerfabrics.com/Blog/Baby_rings.pdf
of course, you might need totally different measurements if you make those rings, but i bet you can figure it out!