If you arrange the woofer and tweeter side-by-side, instead of one on top of the other, you'll have to live with poor horizontal off-axis response.

With traditional vertical stake, it assumes you're head will be at a certain height, but allows you to move side to side with little change in response. Putting the drivers side-by-side will allow you to stand-up or lie-down on the floor to listen, but limit your side to side listening position.