I'm testing this design with arcol hot end for a while. Greg you are right I have some issues because of the two mounting holes. arcol hot-end has 3 little legs what should be hold it stable against the extruder block. But because this extruder block is thinner then the original. the third leg is in the air. what can cause the hot end to tilt a few degree. If I size the base of the extruder block 4mm wider that would fix the issue. So version 2 coming soon.