mamawrobin, you guys dont' need me .... you got it covered very well!
I get a lot of questions about "air". I honestly don't see the "air" because once I put it on the cake and Melvira it, it looks super smooth.
However....... I recently reminded someone that dream whip is a "whipped" cream topping mix. And what makes "whipped" cream light and airy is when we "whip" air into it. I dont' see it .... I dont' have a problem with it. I *DO* know it looks more "air-holey" in the bowl than it does as the final version on the cake.
Also if you make it a day or two ahead of time and let it just sit, it will "settle" those air pockets you see right out of there. I just beat it a little with a big spoon to reblend everything and it's even better than day one.
With any recipe, if you add more liquid to the original recipe, you really need to offset that with more dry. So adding any kind of puree is going to throw the liquid/dry ratio off so use less milk or more sugar.
Crusting is a ratio of sugar to fat. If you increase the fat, you have less crusting. Here's how I remember: Fat is slippery .... adding more fat will make slippery icing ... slippery icing will slide off of the cake, especially in heat. Which is exactly the problem I always see when people use 1:1 fat/sugar ratios.
With this icing, I can even add more milk to make it thinner (like for crumb coating) and it will STILL crust fine because I haven't changed the fat/sugar ratio.
Mamawrobin ... keep up the good work!