Publishing similar but much longer article "again" in different journal?
It depends on what you mean by "flesh out". If you mean "waffle a bit more, add some detail to the introduction and discussion" then the answer is an emphatic NO. If you mean "add some further analysis that uses the original manuscript as a starting point and explores a different, previously undiscussed angle", then the answer is a hesitant yes, but it begs the question of whether it would be more effectively presented as a single, comprehensive paper.