Does anyone have one of these stabilizer bars (specifically the BSBF-1 - the one that is for attaching to the downtube), and could tell me what the thickness of the steel is?

I'm designing a custom part similar to it, and I'm curious what thickness it needs to be stiff enough.

Also, does anyone know what that 3rd small hole is for? I didn't see any pictures where people used it for anything.