Wow, thanks for the quick response!!!
The subfloor is not exposed from above; only from underneath in the basement. They glued and screwed the subfloor to the joists. I'm not exactly sure how many screws were used when they screwed it down.
I was actually doing some research and came across this document.
On page 5, figure 13, is what I was doing. The plywood was getting to be a pain because it was big. If I could use 2x4's (like figure a-a), it would be easier, but I don't know if that would fix it.