I got my Mugen 2.
It can fit on DFI LP DK x38 T2R without extra doing, when wider side is
NOT facing the rear case fan.
If you want to mount it so the wider side faces the rear case fan (like i do), you need to cut very small part of the northbridge heatsink, actually the corner, because heatpipe is stroking it. After this Mugen 2 fits perfectly
.
If pics needed ask.