I'm not very familiar with Magic Lantern - what exactly is it and what does it do with regard to clipping?
You install the software (it sits on top of the Canon firmware) and also load it on each CF card that you use. Each card has to be activated in the camera (made bootable), otherwise you go back to the Canon firmware.
It was designed for video users, but there are several features that make it useful for stills.
-focus peaking (I don't use this much as if I'm looking at the back screen I may as well use live view)
-on screen clipping warning. You can have an on screen histogram with separate clipping warnings for each channel (little red, green and blue dots), and/or zebra stripes. It seems very accurate if you want to ETTR
-auto hdr. Decide whether to start with the shadows or highlights, press the shutter and the camera keeps shooting until the complete dynamic range is covered (not suitable for action as there is a lag between each shot while the camera decides whether or not to keep going)
-auto focus bracketing
Lots of stuff.