My pumpkin pie hardly ever firms up correctly. I'm using a recipe out of Joy of Cooking. . . what are your suggestions for a firmer pie? more eggs? less eggs? more cream? less cream? evaporated milk instead of cream? better temp or cooking time in the oven? graham cracker crust instead of butter crust?

i follow the recipe exactly every time, so i think it's just a bad recipe, but i don't know what to change to make it better.