Thank you for writing back to me and the kind words. 36" X 40" will handle most any heat pump. A slab is a lot of work. Looks nice though. Patio stones and some play sand as a base works too. My feeling about the sun is that if a sunny spot is less than 10 feet from the equipment (water pump, filter etc.) then put the heater there. If it is over that then forget it as the heat loss from the pipes will negate any gain from the sun.
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