I have a few more things to add to this. The hot tub dealer says that the joist spacing required is 12" o.c. As stated above, mine are 16" o.c.. Could I just double up the joists under the area where the hot tub will be? Or should I just put one in between the existing joists (making them 8" o.c.)?
And regarding the footers for support beams, could I just set 4x4 posts on dekblocks (maybe bury some and level)?