Regarding the RMH bench, I live in a mobile home and weight is a concern. Yes, I could shore up underneath, but my 74 yr old body says, "Shut yo mouth, boy." So I've been searching for lightweight thermal mass ideas. I've run across experiments w/ salt (as in water softener salt) and bulk talcum powder. Soapstone is the hard version of talc. Has anyone tried either or both of these?