Yes the black heater pads were experiements using domestic under-floor heater elements, the first one which was the huge black mat (1m square) utilised heater cable set in a mesh although later on i'd cut that away and tape the cable directly to the mat and make a smaller version.
The other iteration would utilse an under-floor element but unlike the first that used cables
i went with a system that was 1mm thick which was a copper conductor set in plastic film.
I concluded the heater cable was far superior to the plastic film in terms of maximum heat (around 80 degrees c vs the film' max of around 35 degrees c and also the time taken to reach maximum heat output but i still wasn't impressed by the time taken with the heat cable tbh.
Hence the silicon rubber mats, these have tungsten elements running through them and were rated for 200 degrees c although the controller boxes i made were limited to 100 degrees c plus anymore than that and you'll start to change the chemistry of the resin.
In a nutshell the silicone mats would hit 100 degrees c almost instantly, obviously i'd dial in what i wanted temperature-wise via the controller boxes but overall they were way more practical as you could get alot more done over the course of a few days.
The 'ingredients' for the my mats were as follows (from outside to in):
So outer layer (the bit you see on the boats hull) edpm roofing rubber with butyl tape taped all around the edge to secure on the hull. Then a layer of 6mm depron with foil taped to it to reflect heat inwards towards the hull then the heater cables
taped to that then breather cloth over that with a heat sensor taped inside to record
temp and thats it.
The pictures tell you all this, importantly you'll need to build a thermostat control box to control temps as you dont want to fry the hull just dry it, google
'ATC 800' and thats the brain i built my control box around , very simple too.
Hope that helps