Ohmigosh, keep the coconut--that's the cake my mom's been talking about all these years!

And now for the questions--i can't help myself, I'm curious about everything and have to know how/why it works 

For the cake: 

I see that the recipe calls for 2 1/2 c flour, and 4 1/2 tsp baking powder. My instinct to get more loft was to add more baking powder! Yet every website I read about leaveners and cakes says "1 tsp bp to 1 c flour, because too much will make your cake deflate." Can you tell me why it works in this recipe, so I can get a feel for when it's okay to use more vs. not okay?

You mention that it's a delicate cake batter, easy to overmix. I have a stand mixer with both paddle and whisk attachments, a hand mixer with both standard and whisk beaters, and a plain ol' whisk with good ol' elbow grease. Which would be my best choice for blending this with least chance of destruction? 

How does melted shortening vs. vegetable/canola oil affect the outcome of a cake?

My 9" pans are the Wilton dark-colored metal non-stop. Will this affect the baking in any way? (I always grease and flour anyway, I don't like trusting to chance)

Do you generally place the rack dead-center in your oven, or do you use the two racks to divide your oven into thirds, and bake on the lower one?

For the original frosting: 

I see that you mention keeping the frosting refrigerated, so it doesn't weep off the cake. Again, same instinct here, and my preference (I'm weird, I love chilled cake!). I see so many people who make 7-Min. Frosting complain about the exact opposite, that refrigerating makes the frosting melt apart. Is there a slight difference in this recipe that allows it to hold up well in the fridge?

For original & SMBC frostings: 

Is it possible to use liquid egg white for either of these, if I don't have shell eggs, or want to avoid leftover yolks? (We use egg substitutes as our "regular" eggs, so that's what I usually have on hand.)

Sorry for the third degree of cake making...I just seem to have better luck when I actually understand what I'm doing, LOL! 

Haha, Paws, you've come to the wrong person!  I don't know the science behind any of the elements of the recipe.  I do know that using the Crisco instead of oil or butter is what gives the batter the gloss.  It is probably responsible for the lightness and fluffiness of the cake, since it does the same in biscuits and pie crusts.  Butter tastes better, but just doesn't give the same light texture.

Your dark pans will definitely make the cake bake faster, so start checking at around 20 minutes.  I always start checking before I think the cake is actually done.  As for the baking powder, it does seem like more than most cakes, but I do have other recipes  with just as much.  I was surprised to discover that the Brits add a teaspoon of baking powder to a cake recipe using Self-Rising flour, something we do not do in the US.  I tried it for Victoria Sponge (a British recipe) and it works beautifully.

I mix in my stand mixer using the paddle.  Just mix on a slow speed and just until well mixed.   In addition to shortening and flour in my pans, I use a circle of parchment or wax paper in the bottom.  Just added insurance.  BTW, I also have the no-stick, dark Wilton 9" pans that I've been using for about 100 years and I always prep them just like all the other pans.  I bake cake in the center of the oven.

As long as the cake is kept refrigerated, I've had no trouble with the frosting holding up for a couple of days.  After that it can get sort of droopy, but it tastes go good, it is worth the aggravation.  I do always keep my cakes covered, so that could help protect the frosting.

I know you can use liquid egg whites to make SMBC (from reading about it, not that I've ever tried), but most people say they just don't whip up quite as well as fresh egg whites.  Make banana pudding out of the egg yolks!  Or curds, or custards!  Lots of good uses.

No problem with the questions.  I just wish I had the answers, but alas, I do not.