I commented in my PAL2NTSC guide about some cases where it is desirable when converting from PAL to NTSC to slow the video to 23.976 fps, but time expanding an audio track with pitch correction (instead of a straight slow-down).

Sony SoundForge has a nice Time Expansion tool. I calculated (wrongly it seems) that the expansion percentage should be 104.27% (which 25/23.976). Testing it the audio was out of sync towards the end.

Should that be an even 104% or more like 25/24 (104.17%) instead? Has anyone any experience with this?