Time Remapping Woes

This is rather urgent. I've just finished rendering a video I've been working on. The general frame rate is 29.97 progressive and I took a specific shot at 59.94 progressive to use for a slow motion speed. After transcoding, I took them into premiere and used time remapping to turn part of the 60p video to 50 percent speed, which I thought would work smoothly since the frames already existed. In playback, it was choppy, but I attributed that to my HDD, which is the significant bottleneck in my system. Anyway, after export the video remained choppy in playback.

I've seen tutorials with time mapping 30p video which must create intermediate frames that don't look good, and I'm wondering if premiere pro did that to me or if you are aware of some other reason for this behavior.

Thank you all in advance,
EZ

Thank you very much, this has fixed my problem and everything is going smoothly now!