Kelp meal is pretty mild stuff, you got to be careful. There was a time when my yields suffered because of kelp meal. They say it won't cause burns, canoe leaves etc. That's BS.
Kelp is only useful for it slow release of K in this SSS recipe.
IMO it depends what kind of base you're using for the concentrate. If the base has coco/coir i.e. Roots Organic mixes, you wouldn't really need to kelp because there just enough K slowly released from coco according to Sub. If the base consists of peat moss like FF Ocean Forest/Happy Frog, I've settle on 1 ounce per 2.0 cu ft bag used with excellent results.