Another alternative is to use the system I use on my Cherry Pi IIIS models. It has all the benefits of magnetic attachment, precision, ease of removing the effector, etc but none of the draw backs. It's also really inexpensive to implement. Basically you have a drilled 8mm ball bearing on the end of each delta rod and a length of Spectra line attached to a spring to hold it all together. It works great.
[forums.reprap.org] (about half way down the page)
Andy
[forums.reprap.org] (about half way down the page)
Andy