After finally upgrading to the G2 extruder (from the old B3 Pico), I was forced to design a new mount for my ABL sensor (capacitive sensor LJC18A3-H-Z/BX) so I could keep using it. This new ABL sensor mount should be pretty universal for Series 1 (2014+) owners. This sensor is capable of detecting the glass/PEI print bed currently installed in my printer. I wired this sensor through the Series 1's PCB's and ribbon cable to keep things as clean as possible.
Sensor I used here on Amazon: http://www.amazon.com/uxcell-1-10mm-Capacitance-Proximity-Sensor/dp/B00542U3M4
6-4-17 Added "mount5.stl" and "mount6.stl" which are both angled a little differently than "TAM_ABL_Mount.stl," so that the sensor will be more level with the platform. I believe mount6 should be the best bet, but it is currently untested. I am still using mount5 with a small plastic shiv in between the mounting hardware to angle it back a bit.
PRINT ORIENTATION: I printed mine standing up (flat surface down on print bed), with a small amount of support material to hold up the overhangs.
I have found that with the current models, sanding the inside of the ring a little bit helps with fitting the sensor properly. I may adjust this on the model in the future, maybe to make it unnecessary to sand.
BASIC HARDWARE INSTALL NOTES:
Disconnect hotend from X-axis PCB.
Remove two lower screws and nylon nuts from X-axis PCB.
Slide mount up into place (over hotend terminal and around PCB) and fasten with two M3x6 screws.
Re-connect hotend to X-axis PCB.
Insert sensor wire through mounting hole from the bottom and carefully "unscrew" the sensor to the desired position (turning it counter-clockwise will pull the sensor up through the hole), and tighten down with provided nuts.
Wiring info may be added later, but can be found elsewhere for now. Should be pretty straight forward though.
DIY MARLIN FIRMWARE MODIFICATION: To make this work I basically just followed Thomas Sanladerer's instructions in one of his Youtube videos, and for now I'll link directly to the firmware section of the video I primarily used while learning how to set this up: https://youtu.be/EcGFLwj0pnA?t=4m35s (I recommend right-clicking on this link and opening the link in a new tab or window, otherwise it will just play the video from the beginning via Thingiverse)
Modified "Series 1 / Series 1 Pro (2015 with Heated Bed - v1.3.0)" Firmware with ABL pre-configured: https://goo.gl/AHRuvD