I have found that adding an extra 2 tbs. cooking oil to any batter will result in a superior texture, that is, more moist and tender. Also, to give cake more rising ower, rely more on the leavening agent (baking soda/acid or baking powder) to cuase the cake to rise rather than on the air beaten into the batter. I usually add 1 extra tsp. of baking powder to the recipe. However, by adding the extra baking powder, that cake may not have enough substance to hold together well when sliced. My cakes have actually come out too tender so that they wont' hold togeter when sliced. To counteract that, I add 1 extra egg to the recipe. By making these modifications, my cakes come out extra moist, and tender.
Don't be afraid to experiment. Cakes are not as complex as many people believe. Once you understand how different ingredients contribute to the final quality of the cake, you can pretty much create your own cakes, using just a basic ratio of four-fat-leavening.
And remember that leavening can be produced by using baking soda (alkali) and cream of tartar (acid), or baking soda (alkali) and yougurt or buttermilik (acid), or acidic fruits and juices such as apple, pineapple, strawberries, basically any fruit with a sour componant, and baking soda. The final leavening agent for cakes is baking powder that has both the acid and alkali ingredients together. I prefer double-acting baking powder as it starts to leaven the batter as soon as it is made wet, and then has a second leavening action that doesn't start until heat is applied. This results in a lighter final product.
Cakes are simply oversized pancakes with flavorings and more sweetener. And remember, that if you add the normal ingrediants, plus acidic fruits, or even more cocoa powder (again it's acidic) you will need to add more alkali (baking powder) to ballance the chemical ratios.
After that, it's a piece of cake
(pun fully intended).
Seeeeeya; Goodweed of the North