cluelessgoon, on your Langster do you still have the original/stock cranks on it: Sugino RD2? If so, when paired with the stock BB (103mm), it will create a chainline of 45mm. If the Shimano BB is said to create a 43.5 chainline, it would seem that it would push your 1.5mm further out, creating a 46.5mm chainline.

HOWEVER, I suspect that if you move your chainring to the inside of the crank spider, it will create a 42mm chainline.
I suspect that this will occur, because it has been documented that the SUgino RD2 cranks, when paired with the recommended 103mm BB, will create a 45mm chainline. When mounting the chainring to the inside, it seems the move the chainline about 3mm, the thickness of the spider on the chainring and perhaps half the width of the chainring itself, creating a 41mm chainline. I haven't moved my chainring to the inside so I can't genuinely be sure of that. In (my) theory if you do use that Shimano BB, it would create a 42mm chainline.

If anyone can refute this to be truth I would love to know. The only part in which I am unsure of is, what chainline you will get, when the chainring is moved to the inner part of the cranks.