This is a truly awesome setup - really like it. One small nitpick about the instructions PDF - it says that 20mm tubing fits the heatsink by default, which I don't think is quite correct as the heatsink OD is 25mm? I'm super interested in your switch over system. I can see how it all works, I just wonder how reliable the last little bit where the hotend has a stub of filament that reached up to the hob which then has to be pushed down and though the hotend by the new end of the filament is? You must have have a very well constrained system for it not to buckle/wedge up at that point. I'm impressed! What are you printing in there?