Yes, thx Phil
. Lenses can be stacked. But more than two has poor image quality. I tried three Raynox 250 and the dof was razor thin with many aberations. Also field of view doesnt change so much (in compare with two rayxon 250 stacked) - from 4mm to about 3mm. The best solution for very high magnification in my opinion is Raynox 250 + 250, or Raynox 250 + 150 (lil bit less magnification, but also lil bit better image quality). In this combinations is image quality still very good (for digital compact).
I stack lenses just using the snap-on reduction which came with the lens. But step-up and step-down ring reductions for safer mounting (snap-on isnt very good solution) are on the way ...