I had a job a few years ago that was shot HD @ 23.976 but the only way I could handle the sound post was with a standard def ref picture.
So the OMF was loaded into the system (dSP) into a 29.97 sequence. Importantly it was non drop to match the 23.976 sequence. It worked perfectly and the final mix matched back to the 23.976 sequence because real time was maintained. Changing to drop frame would have stuffed it up. Do a test because the audio post system may not like loading a 23.976 OMF into a 29.97 project.
Not sure how Virtual Katy would handle changes to frame rate. There was reversioning which I had to deal with. I used Cinema tools to make EDLs of both cuts in 29.97 from the 23.976 originals. I then used Editrace (which is an online service), to compare and make a change list. This is the same as Virtual Katy although it is only EDL based. You pay small fee for each EDL change list generated.
This made it frame accurate to reversion. The rules are simple- match real time, use reference pips at the head and tail of the OMF and the mix should be totally in sync.