Hi Salvo,
We have gotten around this issue by using a Third Party AutoCAD add-on called PVCase. Fantastic solar design tool. I'm currently developing sites upwards of 1GWac/1.3GWDC. Along with developing the full Solar design (Layout, cables, blocking, civil assessment, shading, etc.) it can generate .pvc files for your layout including shade objects. I'd urge you to look into it. www.pvcase.com and see Ground mount option. They also have Roof Mount that exports to PVsyst also. Good luck!