Yep, that looks a lot more reasonable.
And with that design, whenever you reach a new level in the relevant tech (engine tech, engine power modifier, fuel consumption, missile agility and warhead) you can just take this design, leave the values as they are and research the new missile. You'll have a missile of the same size, which is simply a bit better, depending on what tech you get, if you don't want to fiddle with an entirely new design, that is.