Here is my FT-5 endstop. The stock endstop is pretty bad. I went for a solid yet simple design. I made sure it was easy to print, solid so that it will give good repeatable layer heights, and print with no support material.
EDIT: This mount is now being recommended for use in the dual-Z mod.
Details here: https://www.youtube.com/watch?v=txZ5YuRMAzI
Start by removing the bolts and nylocks from the right rear LM8FLUU on the bed. Press the nylocks into the nut recesses on the new lower endstop mount. Insert a 5th nylock into the recess at the other end of the new lower endstop mount. Slide the lower mount around the 8mm smooth rod and up over the bottom of the LM8FLUU making sure the screw holes line up. Reinstall the bolts back through the flange of the LM8FLUU and into the new lower endstop mount.
Next, remove the endstop from the old mount and install it onto the new upper endstop mount. Using 2 M5 10mm bolts and 2 5mm t-nuts mount the new upper mount to the extrusion above the new lower endstop mount. Route the endstop wires through the new upper endstop mount and plug into the endstop. You may need to lengthen these wires in order for them to reach.
Thread a M3 25mm bolt up through the bottom of the hole in the new lower endstop mount and through the nylock you installed earlier. Thread an additional M3 nylock onto the end of the M3 25mm bolt so that the top side is flush with the end of the M3 25mm bolt. This will give the endstop more surface to contact. Adjust the new upper endstop mount so that the M3 25mm bolt lines up with the switch.
Adjust the endstop height by threading/unthreading the M3 25mm bolt up and down in the new lower endstop mount.