Another thing tht comes into play here is WHEN you set the bombs. When using them, you need to lay them with the assumption that your opponent will try to approach on ground, no when they are already doing it. When I fight meta knight, I lay bombs in series with the assumption that he will try to dash through them, hence why I lay them about a second early. Normally he runs into them, and if they blow up before he reaches them, he still gets hit by the after-exlposion. Lets also not forget that if he does manage to dash past them you can either drop one where you are and stay there so that when he grabs you, it knocks him out of the grab, or you can drop one and DI towards him so that you end up behind him when he tries to dash grab. it works out pretty well.