I had hesitated to try this for so long, but finally today a brave EOSHD reader sent me a tweet saying he had fitted his BMCC Speed Booster (with protruding rear-glass) on his GH4. It just goes straight on. First a BIG disclaimer. Speed Booster adapters have adjustable glass which can sit closer or further away from the sensor to fine tune infinity focus. On some adapters this will mean potentially it may clash against the inner housing of the mount and be damaged on a Micro Four Thirds stills camera. Therefore I do not take responsibility for any loss or damage if you try this.