Had to deliver some spots cut in Premiere Pro. The delivery required 29.97, but the spots were cut at 23.98 matching the source. So… here’s the best way to do this.
Step 1 – Export ProRes 422HQ versions from Premiere
Step 2 – Import the masters into Final Cut Pro X
Step 3 – Do the rate conversion In FCP X, because it works as well, and often better than a Terranex
So that’s it, 3 easy steps to getting a high quality rate converted master from Premiere
Final Cut Pro X Babbling 
So can one assume you’re using the “Rate conform” parameter? Is that what you mean by “rate conversion”? Since just putting the 23.98 footage into a 29.97 timeline and exporting really wouldn’t make for a great result.