Many thanks!  Good advice.  I was looking at the Tyvek then followed a link to the polycro so there are options.  My druthers, however, would be a NEMO footprint.  At my age and physical challenges, I don't see myself doing through hiking (although I would like to revisit the Long Trail in Vermont) but some section hiking is clearly possible.  And from what I've read, the NEMO gives up some sturdiness for lightness so a footprint is essential as you noted.  


Again thanks for the help!