Short story: After install, no boot; found it would boot only with a sodimm on channel 1 and nothing on channel 0. Both sodimms worked on channel 1, neither on channel 0 alone or with the other in channel 1.
After spending a couple of weeks troubleshooting, got an RMA board, hoping that would fix it, since it seemed pretty obvious that something was wrong with channel 0 and the memory was fine - but apparently not! Same exact problem with the new board.
So, apparently the 16 just doesn’t like the T-Create Classic memory in slot 0.
I’m now ordering some of the tested memory to see if that works.