Wooden Hot Tub Platform

I need a sturdy wooden platform to support a hot tub. The platform is functional and won't be visible, so aesthetics are not a priority.

The hot tub is 7'x7' (49 sqft) building pmatform underneath what size wood joists are needed
Ive calculated a total load of live load , dead load and tub + water @ 6,450lb making it aprox 130PSF required for this platform deck
2x6 , 2x8 , 2x10? 12" oc probably was panning on using 9 concrete tubes 12" diamemter sunk 4 feet deep into the ground as the deck is elevated apox 12" off the ground. Its a deck platform for a reccesed hot tub. I wil be buodling the top deck around it after its palced a plan for thays not needed just the hot tub base 7'x7'
Requirements:
- Constructed from durable wood
- Sufficiently strong to support the weight of a hot tub 130PSF


Ideal Skills and Experience:
- Carpentry
- Experience with outdoor wooden structures

Please provide a bid with relevant experience.