Grumpy_Mike:
The point I am making is not that it is imposable to make your own it is just that it is not easy to get it right first time. Better men than me have failed at that.
That's discouraging. The implication is that there's no reliable way to design this board and be confident that it will work, other than the empirical (and pricey and time-consuming) approach of building it and seeing if it fails, then trying to figure out why.
Or pay the premium for a pre-packaged DC-DC converter, of course.