After calibrating the three towers the nozzle was to high in the center. I measured the DELTA_CARRIAGE_OFFSET and changed it from 22 to of 21.5 mm in the configuration.h of my firmware. If your noozle is to deep in the center make this value larger. This is necessary because the theoretical values in the firmware didn't match up with the actual printer and so the inverse kinematic didn't work correctly.
It is importand to fix the endstop-trigger M3 screws with glue. Bowden extrusion needs patient fine tuning. Also fix the Bowden Gear, it got loose and so retraction was completely useless resulting in very ugly prints.
I had a crash with the original fan design so I uploaded a new mount.
My BOM ist uploaded
I am now using a J-Head MKV extruder and getting much better results with it, seems like the heating chamber in the makergear extruder is to big for bowden extrusion.
The J-Head reduces ooze and has no curling at all.
Use the Repetier Firmware, it has a native support for rostock printers, set the acceleration to 1500 for all axes, and jerk to 15mm/s to prevent lost steps.
Set the start and end speed for the extruder to 100mm/s.
I also strongly recommend the use of Repetier-Host + Skeinforge for slicing, the dwindle feature works wonders fighting ooze.
I uploaded my basic skeinforge settings just copy the folder under C:\users\yourusername\, temperature must be controlled manuelly, same goes for cooling fans.
I also recommend using a mixture of 3 parts water and 1 part wood glue on the glas for much better adhesion of the first layer, it can be easily removed with a sponge and warm water.