I just bought a used Craftsman tablesaw with a 24/24" fence and have already
had to fudge a 27" cut. It would also fit my work area better if I moved
the rails over to be 36/12".

Is there a sound reason not to do it? All I can think is that the rails
aren't rigid enough to go that far without support. If that's it, would
adding another wing help any, or is it vertical support that would be
missing?

Thanks.