Hey Jeff
I looked into the modify you talked about, and found this:
The upper one is WGA, 240 fps. In the modify ->interpret footage, it doesnt change the FPS, video or audio.
The lower one is 720p, 120 fps. In modify --> interpret footage, the FPS is changed from 120 (as seen to the left) to 60. If I change it manually, or by "assume this frame rate: 60", the video runs normally and not slowed 2:1 - But the audio is off sync because is doubles the speed.