Thank you very much for the quick answer.
The big advantage of this design in my opinion would be the low moving mass in Y-direction because the motors of the X-carriages are fixed to the frame.
I tried to get the design to work with Marlin but Marlin says when compiling the COREXY with Dual X-Carriages doesn't work.
I am currently using Repetier as my firmware. I could set the motion control in the firmware for the 1st X-Carriage to work perfectly. But when I tell the firmware that I want to use dual-X I can't get it to work :-(
I use a Rumba Board with two stepper-driver extensions. The two stepper driver extensions are used for the mirrored z-axis stepper.
For understanding I have attached a drawing of the belt layout.
Is Repetier V2 already usable?
Oh, that's so sad. I have already rebuilt everything :-(
OK, what kind of board should I get if I want to use the V2 optimally? Would the SKR V1.3 / 32bit board be the right choice?
Is it safe that my belt layout will work with a compatible board in combination with the V2 firmware?
Can V2 BLT and TMC2130 work with stallguard?
OK, what kind of board should I get if I want to use the V2 optimally?
I'd suggest Ultratronics PRO. It supports 7 motors, has 32bit CPU and lots of other cool features. Not sure though if CoreXY support for it has been implemented in V2.
...Talking about CoreXY - during the last 3 years I went full circle - from Cartesian to CoreXY with 2 belts then to CoreXY with single belt, then back to Cartesian. While everyone gets excited about simplicity of CoreXY kinematics (including myself in the past), the biggest issue they have is the length of the belts. With small printers that may not be a problem, but when you go bigger, and IDEX usually has bigger than average print size, then you may start experiencing print quality degradation. I don't want to discourage you, but this is something you may want to consider in your future projects.