Building narrow deck

I'm building a deck on the side of my house. it will only be 4'6" wide. I'm going to make it a floating deck and use those Deck Blocks. My question is, in that 4'6" width, how many blocks/joist do i need? I was thinking 2 or maybe 3 at most since it is so narrow. I plan to run the joist long way, and then place the decking boards across the 4'6" width. Any suggestions? The deck will be narrow, but about 50' long.

Building narrow deck