Many kernel/module features have co-dependencies on other features that may only become apparent when you try to do a build and/or when you try to build or to install modules.
"diddle with the Makefiles!" Assume
that they are correct. Your objective, after all, is not only to make sure that the system compiles, but that it will run!
"Getting some sleep" is definitely a good idea. It'll still be there
All of the systems that I have built with IPV6 support also
had IPV4 selected, and who knows, this may be necessary. "If it works," the "extra" code can easily be ignored...