Can you use four whitening strips at once to avoid them only covering some teeth?

I've heard that with crest whitening strips they only cover about six teeth on each row... Can you just use two strips on each row, like two top and two bottom, so that they cover twelve on each row..? Or are they specially designed to fit certain teeth..? Thanks!
--------------------
You ain;t into whitening.........your into dissolving your teeth! These things contain chemicals be careful! I wish I had the teeth you are counting and would hate to think yur numbers would be reduced to mine too early in your "I wanna be whiter than white" life!
Source