Can you help me get my cream pie filling stiff enough? Everytime I make a pie, I get a different result as far as the stiffness of the pie.  I am trying to perfect coconut cream pie (and other cream pies).  

I have been researching Shirley O, Corriher and Harold McGee's work, and understand that the alpha-amylase in the egg yolk must be deactivated by boiling for a short time (although I also saw things like "approach a boil" to keep from breaking starch bonds).  Otherwise it digest the starch as in the cornstarch, flour or tapioca starch.  I understand that once the granules burst and release the starch chains and bond, that the process will start to reverse after the cream reaches its thickest point.  So, I am careful not to stir too much, etc.  I researched the different starches and found that cornstarch is not very heat resistant, so I looked into flour and tapioca (cassava) flour or starch.  I don't think I have looked at arrow root as much.   

OK, what about the sugar?  Will too much sugar make it runny (I did try a recipe with less sugar).   What about the milk?  I use whole milk.  Is there something with the milk?  Do I need to use cream instead? I have read about using gelatin, but am not sure I want that consistency.  Surely there is a secret so that the pie will come out right every time.  HELP!
My coconut cream pie recipe uses milk (2 cups, whole milk gives a creamier flavour), 6 eggs, 1 cup sugar, and 2 tablespoons of gelatin (and coconut of course). It doesn't go like jelly, it has more of a silky consistency.

You divide the milk thusly:


2/3 cup, sprinkled with the gelatin, whisked, and left to soften for 5 mins
1 1/3 cup to make the 'custard'


Once the custard is made (i.e. sugar whisked into egg yolks, hot milk poured in after tempering), simply whisk in the gelatinised milk. My recipe then calls for cream and the egg whites to be folded in (after cooling) to lighten the whole thing.