Thanks mate. You obviously spotted my deliberate error, then, measuring the centres with the head upside down?.....Doh !
Hence the confusing references to " upper " and "shorter " !!!! ( Just threw that in to see if you were on your toes, really, ahem.....). Appreciate your efforts on my behalf, though, thanks. It would help, as one of our big bike jumbles is coming up this weekend at Kempton Park, and if I have some idea of what I'm looking for, it will save me wasting my hard earned cash.
It would look good with twin carbs, though, and I already have several monoblocs, so you never know.........!
All the best
Norman