When a large area of over-development retains most visual characteristics typical of smaller cumulus, favor upwind or up-sun edges of cloud masses and their shadows.  Clear air upwind of such development can offer strong, sometimes amazingly smooth lift – but possibly only for a short time.  The very same airspace also can suddenly become a terrible sinkhole.  If you decide to soar near a large or growing cell, do it cautiously and quickly, with a plan of escape always in mind.