4cM works well with strong nt: - you don't have the uptheline vs walsh dilemma - The weak nt hands can still preempt a bit by opening 1M rather than 1m - you don't have the light 2-level responses which are the weak point of Acol You could play: 1c natural or 18-20 bal 1d natural or 12-14 bal w/o 4cM 1M natural including 12-14 bal w/4cM