due route made a very good point about optimal chainline having everything to do with your shifting sequence preferences, i.e. which gearing combinations that you would want to put emphasis on being smoothest.

I nearly center my freewheels with my large chainring whenever I tinker with chainline, since I only ever use the largest few cogs with the small chainring. I thus can use the entire spread of the freewheel with the big chainring without any critical extreme of chainline causing noise, friction or other problems.

Since I also employ cheapskate methods, I keep a variety of lengths of bottom bracket cartiridges on hand for test-fits, many of these being discards with rough bearings. I can thus determine what if any bottom bracket parts that I might have to actually go out and buy if I don't have the exact length part I need.

I've fitted Ofmega spindles with both ISO and JIS-taper cranks, so as I recall Chas often saying, "if it fits it works" or thereabouts.