About this 3D model

I own a rapman (bits from bytes laser cut reprap derivative) and looking at many designs I like the extruder this guys made very much. The extruder is divided in two parts (linked with 2 screws) - the "drive" part where a stepper driven shaft grab and push the filament - and the "hot end" part that is, well, melting the plastic. After many kg's of filament (abs, pp, hdpe, pla) trough the hot end from bfb I never had issues with it and as they sold hot end as a separate "part" I figure one can mount it to the Mendel using the pinch wheel drive and the bowden cable as the "other part" of the extruder assembly. This is a good idea but a hot end from bfb is ~40mm in dia hence I had to modify the carriage a bit (just drilled a big 40mm hole in them).