Fortunately I came across this great Hackaday page by Patrick!

He was nice enough to answer questions and help me with my design.  My previous 2 layouts were failures, shutting down after only <4.5W output.  

I notice the recommended inductors for this thing are >4A!  for only 2A output current I thought this was very strange..

Anyway, I designed this new proto board to run further testing.  I'll report back!

So far I learned:

*CFF is not necessary.  It is used for large transient load regulation.  The recommended 10pf completely screwed up the output.  A more modest 1pf seemed to work better (both 50v NP0 rated)

*Actual efficiency is closer 80-85%

*ILIM should be tied to EN if unused

*Ground loop layout is extremely critical

Questions I have so far:

Q: GND and PGND being separate makes me wonder if GND should be tied only to signal ground, i.e. the FB resistor?  But the datasheet layout shows them joined so...that's what I did

Q: How will it funtion with a 3A-4A Inductor, rated 2.2uH?

Q: What is the actual sleep mode current draw?

Q: What is the EN pin current draw (wondering if a flip flop might actually be causing an issue driving this)