Haven't seen a Delhezi that size of eleven inches, but yeah, if you can feed the birchir well, it's a possibility to have the 3 inch channas in the same tank. Otherwise, if hungry, the birchir could easily prey on the channas although it can't swim as fast as the channa, it could be successful in an ambush. Birchirs also have varying degrees of aggression, if I were to rate the common ones, Endichleri would be one of the top on the list, Delhezi would be way down so I do agree with Ewe that they could do well in the same tank as your dwarf snakeheads, ah but the proviso, hehe....feed them well there won't be trouble.