I have a bounce issue with my living room floor. My floor is a 20' x 12' Oak strip floor held up by 2" x 8" x 12' joists at 16" OC and I have full access underneath. What minimum size beam do I need to install down the middle with only 3 supports along the entire 20' run to get rid of the bounce? I would like the middle support to be 12' from one end. I'm thinking three or four - 2" x 8" with 1/2" plywood sandwiched, glued and nailed together should be good. Anybody know for sure?