General

[quote=lowmastercal]haiku are 5-7-5 but good job[/quote]

They're not limited solely to 5-7-5. There are some examples of 6-5-7 or whatever.

I'm pretty sure that they might generally go 5-7-5, but it's not a determining factor.

[quote=Exrenbon]I think haiku's are 5-7-5, not 3-5-3[/quote]

3-5-3 is much more limiting compared to 5-7-5. I think it fits better that way.