O.K. -- when we get to discussing baking techniques, I think we've gone a little too far off the kayay-building topic. And is that a DOILIE I see under that cake?!

Just kidding -- nice work, Rehd ;-) You know, a laminated construction (read:layer cake) would be stronger than a single homogeneous substrate. George has data on this on his website. Look for the chart titled 'bulk modulus of various cake mixes.' And as to the foamy fill-coat, I'd suggest you not mix too vigorously so as to introduce air to the mixture, let it set in the bowl for a few minutes to let it react before applying, and keep squeegee'ing until it sets up. Remember that drips and runs are fairly common -- that's what we all have random orbital sanders for...