I have just got PP for a 4kw ground array. The supplier has suggested that the panels be mounted on a "console" which is a plastic tub not unlike a grit bin used on a roadside but specifically used for solar panels. They are normally used for flat roofs provided the roof is strong enough. The ground is levelled 100 mm of hardcore laid down the "bins" lined up and part filled with ballast to weigh them down then panels fitted. The bins are pre angled to give the correct angle of inclination, we are going for 25 deg and whilst not ideal for winter apparently is best for achieving max FIT. I live in a very windy location and this way the wind cannot get under the panels also they are only about 600 mm off the ground which also helps. Details of the consoles can be found on this link. www.renusol.com