A lesson learned: If focusing cloth has 'elastic neck' that wraps around camera back, then the drapery must be breathing. Otherwise it will be hot in the sun and goggles are fogged within really short time.
Apparently my cheap focusing cloth with similar 'elastic neck' as BTZS focus hoods, isn't made such a breathing material.

Too bad that I don't have daughter... and my boy is too young for learning to sew.