Well, I has been a whilte since we had a really new ADK, I almost forgot how to get the boot.wim from the PE addons iso (without installing the ADK). Nothing much seems to have changed: Open the Addons iso, get the 3rd largest .cab file from the \Installers folder, open with 7zip and extract, rename the larger of the two files to boot.wim. I also did a quick "custom PE" test on it, all my PE tools seem to work correctly (Disk imagers, Apply, etc. etc.) Thanks to @abbodi1406 for the links.