In reply to:

both spang and smack would seem to mean precisely or directly in these contexts; although I suppose smack-dab would suggest more-precisely. :)

I've often heard smack used in this sense, spang springs entire new upon me.


Perhaps it's a contraction of "smack-bang", which is rather common up here. I haven't checked its gh score, but my gut says that smack-bang would be slightly more common up here than smack-dab, although only just.