In Search of Sweet Potato Pie

I have fond memories of sweet potato pie from my college days. The ladies at the campus cafeteria downtown made an excellent sweet potato pie that I would treat myself to on dismal winter days. It was thick, rich and substantial. Not too sweet, but definitely not bland. Very satisfying. And way better than pumpkin pie.

Its been awhile since I've made sweet potato pie at home, so I decided to start with what seemed to be a tried and true recipe from All Recipes. Although I followed the basics of the recipe, I made the following modifications:

• I used four small sweet potatoes instead of one large one. Using one sweet potato to me is like using a single clove of garlic--why bother?
• I used 3/4 a stick of butter instead of a whole stick.
• I subbed 1/2 of the white sugar with brown sugar.
• I used soy milk instead of regular milk.
• I used a store bought graham cracker crust. I love these and almost always prefer them to a "real" crust.
  

The resulting pie was tasty, but a bit too airy and mushy for my tastes. Even though I had enough filling for each slice of pie to seem substantial, it lacked the heft and weight I was after. I think next time I might try subbing sweetened condensed milk for regular milk. Any other suggestions for baking a killer sweet potato pie?