Increasing frames on fast-forwarded footage (Mac SVP with VLC)

For dumb reasons I need to increase the frame rate on a fast-forwarded clip. The clip has been doubled in speed in Final Cut and exported in 24 fps as an MP4. Strangely, SVP won't even attempt to increase the clip's frame rate (the High Frame Rate Index in the Performance Monitor shows no activity while it's playing). What's really confusing me is that SVP will add frames normally to the same clip with the same 24fps file type, but only the NON-fast-forwarded version. So does SVP recognize fast-forwarded footage and think there's no need to add frames to it? This would make some sense, but I need to get my fast-forwarded footage to at least 48 fps and then slow it down in my editing program.

I'm a noob and it's possible I'm missing something obvious. Thanks so much in advance.

P.S.: Why not use the original, non-fast-forwarded clip I referenced? Has to do with it being shot with the shutter speed too low, resulting in repeated frames.