Finally hearing someone who sees the OBVIOUS to obstruct 'may be short' 1C! When their 1C bid is 2-7C, 0-5D, 0-4H, 0-5S, and 12-21hcp what do they know? What can they sort out at 3-level with one response to decide partial/game/ penalty? Make them guess especially when the guessing is bad = highly ambiguous, many possibilities. Much changes after passes in an auction. Especially, the likelihood of opponents overheating. They may still mis-bid to wrong strain, or under-bid, but no left field overbid is possible. The same for our side: partner won't overheat unless promoting a super fit. So most divergences up or down from expected are effective. 4cM in 3-seat even playing 5cM; 1NT 10-16 in 3-seat; 2C starts at 19hcp; 1C/1D are strong ala Roth-Stone.