A modified version of the YAFSH (Yet Another Filament Spool Holder) (http://www.thingiverse.com/thing:12974) to fit my Prusa Mendel.
With my print, I didn't even have to tie the clamps (feet) of the holder to the rods. The snug fit seems to hold it pretty well in place.
Also took out a little plastic from the center of the spool hub area to save on some material.
This was a rough mod so please excuse the sloppiness, I didn't have time to make the openscad code all nice and neat, but still wanted to share it.
Also threw in that filament guide I have in the picture, in which you will have to drill a hole because I didn't add it in the files.