IVTC question - how to avoid jerky pan scenes

[DRP]

I have a 29.97fps video which I want to IVTC *and* convert to PAL. I know how to do the IVTC in both VDub & TMPGEnc but in both cases the end result has slightly jerky motion during panning scenes. I understand that this might be because I'm specifying a 25fps output for a 23.976fps input, but is there anyway to avoid this?

I note that if I simply make an NTSC stream instead and get the DVD player to do the IVTC while playing to PAL output the same jerkiness still exists.

In all three methods I've tried...

1) VDub to do the IVTC and then frameserve to TMPGEnc
2) TMPGEnc to do the IVTC
3) Make NTSC stream and get DVD player to do IVTC during playback

...all of them produce the same result. It's easily watchable, but there is still some slight jerkiness in scenes with motion in them. Is there a way to stop this happening?

[DRP]

Sorry to reply to own post, but I figure this should be possible to do. I do this conversion all the time with AVI files at 23.976fps. In that case I just use AVIFrate to change the frame rate from 23.976 to 25 and there is no jerkiness in the resulting encoded MPEG. Is it possible to do the same thing after doing an IVTC on a 29.97 stream but before it gets input into TMPGEnc as 23.976?