I would like to add radiant heat to my kitchen floor. I will be using vinyl flooring (with a floor heat sensor to keep the temperature below 85 degrees F). One option is Schluter radiant heat. In their instructions for installing vinyl they suggest pouring self leveling cement over the electric wire mat. In my case there is about 5/8" dip near the doorway so self leveling cement would give me a 7/8" step at the doorway (1/4" plus the 5/8" dip) which is unacceptable. I am wondering if I can use thinset adhesive to glue 1/4" plywood to the electric mat and put the vinyl over that. Another option is to trowel thinset directly on the mat and than apply the vinyl to that but I do not feel confident I would get the thinset flat enough. I have not seen anybody address the problem of not being able to use self leveling concrete.
I also considered the ZMesh low voltage floor heating system which is approved for this type of installation (vinyl over plywood over mesh) but the cost is significantly higher.
Any other suggestions?