Hmm...
Not having much luck so far with subtly changing the tempo flavours of a few completed songs to provide more groove or attitude - the original tempo still sounded more natural to me in all cases.
I suspect what I need to try now is to choose a serene/groovy/edgy/swagger tempo at the start of a new project, so I work with it from the start, to see if that benefits the chosen flavour
Still fascinating stuff though!
Martin