Anything I put on my cakes seem to sink into the cake a little and fondant seems to weigh it down. Should I make denser cakes maybe from scratch?? Any suggestions????? What kind of cakes do most cakers make for their customers.....that will hold up with fondant and buttercream and decorations, etc and still retain shape? Thanks!!

Always let you cake settle before frosting, that was any sinking that happens will be leveled when you frost. Make sure you have a really stiff dam and that your filling is thick enough. And what do you mean by what you put on the cake? If you're putting something on the cake, make sure you're putting support under it, like straws or dowels... Hope that helps!

how long do u let it settle? and in or out of fridge?

Are you following the directions on the box to make the cake, or are you using the WASC recipe? If you are following the box directions, then that is the problem. The cakes are too soft/fluffy to be able to bear the weight of the fondant.

If you don't know what WASC is, it means White Almond Sour Cream cake. You can make it with any flavors, not just almond. It starts with a box mix, then you add extra sugar, flour, sour cream, eggs, etc. It's pretty good, fairly easy, and holds up very well under fondant.

There are several WASC recipes floating around, all pretty similar, some use whole eggs, some only the whites and no oil. Try a few and find your favorite.

Look in this link. It has the two main versions at the top, then below are tons of variations.
https://docs.google.com/Doc?id=df4f9hbq_46cs9f28fs

I have made my last six cakes with either Pillsbury or Duncan Hines and so far I have not have this problem. The cakes hold the fondant and decorations very well. What I think I do different is that as soon as the cake comes out of the oven I use the push down method, by doing this the cake seems to get denser. I also bake everything at 325 it takes a little bit longer. I set my timer depending on the size of the cake pan to either 40 min or 50min and check for done. Maybe you are rolling your fondant too thick? I do not have much experience but I hope this might help. I was forgetting, you also have to be very precise with the measuring of the ingredients. CIAO