Playing fast, hands together?

[Abstract Harmony]

I'm playing Puck, a Grieg Lyric Piece Op. 71.  So far I've only been playing the first page or so. 

I'm having some speed issues, but I'm sure it has nothing to do with with my technique because I can play it HS at about 120% of the tempo it is supposed to be around.  I can play it HT at about 50%, but my coordination completely falls apart when I start plalying it fast.   

Any help would be appreciated. 

[keys]

Playing Hands together is significantly more difficult then playing hands separate. I don’t know of any short cuts. Practice very slowly – at half speed. The coordination you learn in the one piece should be useful in the other, so don’t be discouraged if it takes a long time. You will not have to practice this way for the rest of your life, eventually your coordination will develop sufficiently to enable you to play whatever you like hands together with minimal additional effort from the hands separate practice.