Measuring chainline

is it really that much off though? even 1 or 2mm will look quite off to the eye if you squint down the chain because of foreshortening. 5mm would show a really obvious angle looked at from above, not just when you squint down the chain.

True, it's difficult to be sure, but when I sight along the chainring, the line clearly intersects with lockring thread, not the sprocket thread. Anyway, I'll wait till I get some wheels sorted out before I do anything (hub is currently rimless) - at least then I can cycle it to frame builder to have it checked properly!