If you used the link
101_FotRSUv18_FixPak.7z, then you may have exceeded your download authorization for the day. Try again in a few hours, or perhaps tomorrow. That add-on is not needed for the base mod, but does fix a few issues. I am not certain how Onkel Neal works the download bandwidth anymore, but the FotRSU mod is rather large, at almost 2gig in size.
The
AddInModzPak_18.7z does add some options to the game, as does the other mods on the first page with vickers03's
Fleetboat_Interior: Officers Quarters, and s7rikeback's
Nippon Maru and
Nihon Kaigun add-in mods. Those, for the most part, are the only "sanctioned" mods for FotRSU, though jimimadrids new stuff should work with some care. Just be certain that you start with a fresh SH4 install, outside of a Program Files folder, that you use a LAA-type applet on the SH4.exe, and that you have either emptied the game's Save folder, or created a new one with MultiSH4v1.5, which is also included in the FotRSU mod, along with JSGME in the "Extras" folder. You will have to pay attention to the details in the instructions in each of the add-ins and packages. Let us know how it goes!