Burned my trans up last year due to not having a sprag in my convertor and extended "Spirited" driving, long up hill grades, etc the conv was cooking the fluid without a sprag.
Trans was so hot it melted the teflon rings on the center support and I had DEX 6 in it and I think it definetly handled teh heat better than type f would have but was still smoked.
After getting a sprag added, trans rebuilt and talking with my builder he recommended Trick shift non syn.
Its a type F style fluid and shifts better then Dex 6 he said that the trick shift formula has a better heat tolerance than reg ole type F.
Finished out the season with it and the fluid is still clear and no residue of the dipstick on a white towel.
On a side note I noticed that ATI makes a synthetic Type F.
http://www.amazon.com/ATI-Super-Synthetic-Transmission-Fluid/dp/B0055SC45Q
Someone try it in a ten second and faster car and let me know...LOL.