The crankset is a standard road double fitted with cyclocross rings. I measured the way from the sheldon brown article and came up with about 47.5-48mm, but according to him the correct chainline should be 43.5 like you said... I also noticed that when in the large ring, the chain only appears to be straight when in the outermost three rear cogs.
Should I assume from this that my chainline is "wrong" and that I need the shorter BB? If this is the case could it be the root cause of my front shifting isssues?