Please forgive me if this has been explained before ( could not find an answer)

I tried the HDR function with the frame rate at 48 fps when filming and 24 fps in Final Cut Pro x. I use the procedure developed by Alex4d.
The HDR bit turns out good but the movie itself is choppy probably 12 fps.
I see Newman films and others produce beautiful clips with the 5d mark ii.
What am I doing wrong ? Can someone help me with a complete step by step guide?
I am on a Mac by the way.
Please help
