We reduced the length by 4 ft.

We looked at the options available locally that would work for the deck. Plywood, osb, pressed particle board, all heavy and in need of sealant and flooring(even more weight) to protect it.

I was thinking 1x6 pine boards may work?

A very helpful gentleman at HD asked about our project and preferences, then pointed us towards some toung and groove pine planks. They are much lighter, although they require more support beams than I had hoped.
The pine planks look more expensive at first glance, but after adding the cost of the cheapest flooring I could find (rolls of vinyl plus the glue and trowel to spread it), the pine was cheaper in the end.
