The GTNH fork of Railcraft removed all the other mods API files, which is the only reason why I needed that one. There was classloader Issues I got from Railcraft due to it containing API files in the jar. I eventually found the culprit in my own code and fixed it, but I was not sure if that REALLY fixed the crash, so the warning is still there.
And those disabled tanks are GT5U specific, so they basically don’t exist with GT6.
You can still try to use the old version of Railcraft, and it will probably work, hopefully.
Anyways creating more than one pull request for one project is a major pain in the ass on github, I dont think that I will do anything else after this Thaumcraft related fix I already PR-ed and is somewhat awaiting merging.