We did a test-run pitching on hard standing last September and it was totally successful. The week was a scorcher and we could have been on grass but the day we packed up the weather changed. What a joy not walking round on wet and muddy grass while packing up! As the Karsten was a big outlay, the last thing we want to happen is it getting covered in mud.
We put down two 3.5 mtr square cheap tarps bought on Ebay. Karsten fitted exact. Rock pins all round and we were sorted. We have the inner comfort matting and couldn't feel the ballast underneath. As the trial worked we will buy a heavier duty tarpaulin to pitch on for the future. You just need to check for any large or sharp stones before laying the tarpaulin down.