So I got a crown amp and tech 21 rbi and a skb 4 space to put em in. The preamp will obviously only be attached to the front as it is shallow. The heavy amp I will put on the bottom, and it attaches at the front only. There are two holes on back flanges, but they are perpendicular to the skb rear holes. Are there some 90 degree els I am supposed to buy somewhere, or don't these heavy poweramps attach front and rear to the skb ata racks?