Oh, got it! Yea, that's the only way to ensure that you'll save the required amount. Otherwise, they'll be too scattered out and you won't be able to meet the quota. The standard trap the crowd with 1/2 blockers does occasionally come up, but it definitely seems to be a rarity in custom packs. Also, as you have correctly mentioned, there are creative tricks that you have seen with blockers beyond just the standard and common function of turning lemmings around.