Hi ploneric, I have the same question, but for both shelly EM and 3EM. I have asked official support and my questions and the answer are bellow:
Dear Shelly team,
Thank you for your support. Just few more questions I have 
:
-is Shelly 3EM working with 50 A clamps?
-what is the minimum current when Shelly 3 EM starts to measure accurately?
-what is the minimum current when Shelly EM starts to measure accurately?
-is minimum current and accuracy dependable of which clamp is used, 50 or 120 A?
-----------------------------------------------------------------------
Shelly 3EM cannot work with 50A.
24.57kW is the max limit , which device can measure per phase and total.
---------------------------------------------------------------------
If you find some more information please share it with me.
Best regards.