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OK, finally got it -- I may have been somewhat hesitant to throw my cow into spikes but I didn't realize he was impervious to the damage.  Even now it took some time to get the rhythm, but once I did it was pretty consistent -- Jump, throw, snap up.

Edit: And woot, I completed the game.  I actually only had 6 stars when I got home so I went back to the first snake spring stage to grab the extra star there -- I managed to grab the star by waiting for the cow to fly over the spikes and fall down so I could snap to him and go through the wall.