I think as far as the curved hilt goes, it would be more of a personal preference of the user instead of a requirment for the Makashi style.
(I had read somewhere that the curved hilt in the movie was done because Christopher Lee had trouble gripping the straight handle, some thing about Arthritis, but I don't know if that is truth or rumor).
You will notice though that if you grip the curved handle further down away from the blade right in the middle of the curve, you can change the attitude of the blade by simply squeezing the bottom two fingers, making for very precise tip control, much like some modern sport fencing pistol grips. Alot of the curved one handed swords (Chinese ring swords, Hungarian sabers, etc) had slightly curved grips to allow more blade control when swinging onehanded as it can get difficult to stop the blade or alter its path once your hand starts getting tired.
It looks like to me when Dooku is fighting in ROTS and before, he is gripping with the thumb and forefinger in a circle, allowing the blade to pivot and roll easily in his hand, then applying pressure with the little finger and ring finger to apply quick snapping cuts after the rolls.
The wookiepeedia describes how Christopher Lee is shown holding it, but not how his stand in is actually using it in my opinion. Holding the thumb down the grip limits the ability to roll the blade as he is shown doing in the movie.
I will have to put that in tonight and look a little closer.