okay, here's what we did. We used a car jack (really) and a 4x4 to initially lift the floor boards up...then we took another 4x4, put it in place, and released the jack. We did this in 3 places. This is a 1920 home, so we heard a lot of cracking while doing this...but we drank more and turned up the stereo. But it did solve the 1/8" dip we had in the living room. We used seasoned 4x4...and wood glue on the top, just in case. The base of the 4x4 we covered in silicone to prevent mold and/or decay.