Compact extruder for Prusa i3 and 42YF22GN050R (2engineers) geared motor with shaft support

This thing is a modified version of http://www.thingiverse.com/thing:69342
More parametrised.
This is a drop in replacement for Greg's Wade geared extruder http://www.thingiverse.com/thing:18379 on my Prusa i3.
Filament - 1.75 mm.
BOM
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1. 42YF22GN050R - geared motor
2. MK7 drive gear
3. 3 x 624zz bearings (2 for support, 1 as idler)
4. 6 x M4 washers (around each bearing)
5. 5 x M4x20 socket head screws
6. 5 x M4 nuts (I use 3 x M4x16 without nuts for bearing mounts