I know yellow cake mix has a recipe on the side, but I'm using WHITE with whole eggs and my own flavored exacts for taste. I need to make a shaped cake and a firm cake would do. What do I add to the cake mix and do I change the water/oil portions? Thanks.

Look for the recipe for White Almond Sour Cream cake. This produces the best firm yet moist cake I've ever made. It can be done with any flavor cake.