Stickman - One thing that I know for sure will stiffen a floor is to use good quality ply wood, glued directly to the joists.
The houses in our development were built with that cheapo board made from large flakes of wood.
When I upgraded my kitchen I put reinforcing beams in the basement because we were putting ceramic floors down and I wanted to prevent bouncing.cracking - it worked somewhat.
Then I helped my neighbour replace a high traffic section of his kitchen floor - we ripped up the old floor and replaced it with quality plywood glued directly to the joists
The difference was amazing - his floor is like concrete (i.e. by comparison)
Both houses have joists at 12" centres
Hope that helps
The houses in our development were built with that cheapo board made from large flakes of wood.
When I upgraded my kitchen I put reinforcing beams in the basement because we were putting ceramic floors down and I wanted to prevent bouncing.cracking - it worked somewhat.
Then I helped my neighbour replace a high traffic section of his kitchen floor - we ripped up the old floor and replaced it with quality plywood glued directly to the joists
The difference was amazing - his floor is like concrete (i.e. by comparison)
Both houses have joists at 12" centres
Hope that helps