I have built the circuit as described. However, I can only program the slaves if the 487 is not on the socket and I can only see general communication in the shell when the dcs is running. The slaves don't communicate with the master.
Images of the build
https://imgur.com/gallery/ydAW2gI
Ok, solution : bad breakout board at Arduino mega
But one problem, can't upload a sketch on the slave with usb. Only if I remove the 487 from the socket :(