Sorry for the delay. I just wanted to let you know that your advice got me there! I was in
fact using a mix of BOOTAA64.EFI/grubaa64.efi from different urls. I got lazy, and
downloaded them from different repos and didn't check to make sure I had matching
versions. When I downloaded both the dvd iso and the netinst iso from the same location,
and got the files I needed from them, it all started working.
Thanks for the pointers.