Usually if you place them back, they produce more bass. You can face them down and should net simiar results. If you face them down, you don't have to worry about them being damaged. If it's a sealed box, you can shape it any way you want, just be sure that the internal air space is the size the sub needs. Obviously if you face them down, make little legs on the outer portion of the box to keep the subs off the ground. 
