it seems to me. Clumsy, but easily handled. Water might add 7 kg. They are about 1 meter wide by 4 m long, so the weight is spread out to the point where the psi is almost nil.

As far as hold-downs, you use c-clamps on the upper interconnecting pipes, screwed into the roof. Then you screw small eyes between the pads at about the 1/3 and 2/3 points of their lengths and run a rope or strap through the eyes, tied off at the ends. Idea is that the pads expand and contract according to temperature conditions, so you give them some freedom to compensate.

Definitely go water-to-air, when you replace your heat pump. Via well, or trench - or solar water-heating pad - the "ground source" system is the most efficient method.

paul spencer