Can you put a plastic dropcloth over two picnic tables pushed together and pin baste, etc. outside? No, that won't work because you'd pin the dropcloth to the quilt back. You'd have to have clean freshly painted picnic tables for pin basting. But the picnic tables would give you some space for other parts of the quilting process, especially if you could locate them under a tarp or roof of some kind for shade and rain protection. Just thinking....