When we first studied adjective conjugation in my Japanese class, I kept making the same mistake habitually; I would conjugate the past tense of い-adjectives with でした at the end instead of dropping the い and adding かったです. My teacher would correct me, and now I've more or less started doing かったです, but I still wonder about how "wrong" adjective-でした is.
Is the second sentence straight out wrong and/or extremely unnatural-sounding? Would anybody in Japan conjugate adjectives like this? Or does it possibly introduce a slightly different meaning?