Top seedling at what height / are these strains receptive to topping?

I am just about to wrap up my first grow, which was 5 Chronic by Serious Seed. I was told that this strain doesn't respond well to topping so I never topped.

This go round I am growing four plants total (all feminized) and each is a different strain. Specifically, I'm growing Durban Poison, OG Kush, White Widow and Super Silver Haze.

I know that I will definitely need to top the Sativas. Each plant is around 4" tall right now. When should I top?

Are these strains all receptive to topping? Should I top the sativas, particularly DP, more than once. My height limit is about 4.5-5 feet. I can maybe stretch to 5.5 feet but that's the max.

Thanks.
 
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