We want to put in radiant heating in part of our walkout basement and have a maximum of 1  1/2 inches to work with.  The finish floor will be vinyl.  I found a great article comparing panel products (http://www.chple.arch.vt.edu/CHPLE%20Research%20files/Khanna,%20Amit.pdf) and think I would like to go with the Roth product because it was rated high and it's made from foam insulation which I believe is a good idea for a slab installation.  Has anyone had any experience installing this on a slab with an overlay of luan or 1/4 inch plywood and a vinyl floor?  Any other product recommendations?