Wanted to put a dual extruder on my HyperCube printer (designed by Tech2C) and couldn't find one already designed so put one together myself. Hopefully you'll find it useful. If you make one please post a pic.

This incorporates the capacitive sensor from Banggood: http://www.banggood.com/LJC18A3-B-ZBY-1-10mm-Capacitance-Proximity-Sensor-Switch-NO-DC-6-36V-300mA-p-1098083.html?p=0M281534004802015125

The fan shroud cools both hotends and uses a 40mm fan: http://www.banggood.com/3Pcs-12V-DC-40mm-Cooling-Fan-For-3D-Printer-RAMPS-Extruder-RepRap-Prusa-p-1120862.html?p=0M281534004802015125

Hotends: http://www.banggood.com/1Pc-8-Types-All-Metal-J-head-Hotend-Extruder-For-1_75mm-Filament-RepRap-MakerBot-p-1023514.html?p=0M281534004802015125

Distance Between Nozzles is 24mm and the inductor sensor is centered between the two nozzles and sits back 21.22mm.

If you have any questions, let me know...