Extreme Macro Using Stacked Lenses

[hellfragger]

I read that macro photographers stack an inverted wide angle lens over a telephoto to get 10:1 or greater magnification. I wonder if any of you have tried that ? I am curious as to how they choose the telephoto and wide angle lens ( on what basis ) and how do they calculate the working distance ? ( or is it just hit and trial ? ) is it advisable to do the above stacking as a cheap alternative ( like if one has both wide angle and telephoto lenses, but does not want to spend on the MPE65mm ? )