Sorry for the late reply, but I revised my mod quite a bit.
My original design was quite laborious, but I found a more elegant solution based on ultiarjan's suggestion:
www.thingiverse.com/thing:4873659
I just made two small accessories:
1) tube-holder: reuses the bowden-tube as cable-guide
2) Y-endstop-extender: BMG stepper motor will crash into the UM2 housing without it
You will also need:
- "Ultimaker 2 BMG direct drive mount" by Tigerhawk60 (www.thingiverse.com/thing:3798359)
- Bondtech BMG extruder
- "Tinker-Firmware" by TinkerGnome (github.com/TinkerGnome/Ultimaker2Marlin/releases)
- V6 groove mount compatible hotend (24V Heater Cartridge, PT100 Thermistor)
- small piece of 1.75 mm bowden tube
- custom slicer profile
I would also recommend to print everything from ABS or similar temperature stable.
There is also a aluminium head assembly on AliExpress, but be careful, you may have to modify (drill/mill) to get it working. Also it's quite heavy and the included linear bearings are trash. In retrospect I would recommend to start with a 3D-printed one...
Prints like a charm now (even flexibles).