Summary well, i wasn't very happy with my Rostock so I modified some parts -the platform (see original here http://www.thingiverse.com/thing:31642 ) I added some more clearance for the hex nuts so now pushing them inside, the plaform doesn't crack -head mount top has a 9.3 mm hole for the pushfit bouder mount -ventilator mount is for 3 pieces of 25x25x10 12V ventilators. I had some problems with the all metal j-head extruder cooling so i added 3 ventilators -the arms on my Rostock where very flexible (glass fiber 5 mm diameter arms)... I have made some rigidizers for them, some kind of push-snap-fit stiffeners. This need some work after printing, you must cut off the surfaces with the ellipse holes, you will end up with 6x 220 mm long stiffeners to push on your arms The groove for the all metal j-head extruder on my Rostock is an 4mm alluminium plate, inspired from here http://www.thingiverse.com/thing:788096 Instructions printed at 0.2 layer / extruder 210°C / bed 70°C / PLA