If more storage spaces are required above what a selective system can yield, then you may want to consider a double reach system. It reduces the number of aisles, thus adding more pallet positions, but at the expense of reducing your pick selectivity.
Another disadvantage is that it requires a special reach type of fork truck (double-reach truck) which, if not already a part of your truck inventory, obviously adds an additional cost.
We can help you assess if Double-Reach Racking is best for your material handling and storage operation. Just give us a call at 330-788-4081.