Hi,
The SD7 and SD9 models have been updated yet again: Users who downloaded the engines before today can download and install a small patch file. The update consists of a small tweak to the blueprints that allows the engines to be used without having to switch on the Kuju\RailsimulatorUS assets in the scenario editor (the US Loco & Assets Pack is still required!) This neat workaround has been brought to my attention by Dave Dewhurst — thanks very kindly!
You can download the update files from each SD7/9 pack's download page on my website. The updated files are also included in the main RWPs.
Cheers
Michael