When you place several parts in Z-suite, each part has a “cubic volume” that can’t touch another volume. And this cubic volume is far from reality, this means some times you need to put a large distance between parts because of their shape, so it’s not optimized on the plate.
Please allow a closer placement between parts ! 
Hi @Xavier!
Please remember that you can overcome the limitation indicated by Z-SUITE.
I mean that you can place the objects closer to each other even though the software tells you there’s something wrong.
Let me know if that helps.
Kind regards,
Marcin
OK, i always tried to avoid red !
Thanks for this usefull and simple indication.
Xavier R.