I`ve had magura -04 -05 - 06, Echo CNC and Echo SL. I`ve had no problem with leaks on any of these. Also, my best tip for bleeding is: Shimano mineral brake fluid. It keeps the seals tight, bleads easily, and runs lighter than magura blood. As for using a booster with M6 bolts, you can simply drill larger holes in your booster, and your good to go. Keep in mind, that the better the pads / grind are, the less power you will have to use on the lever, which in turn gives less strain on the seals, and the brake will be less prone to leaking! Rant over... Cheers!