So I recently swapped an Acera MTB drivetrain over to a road frame. I used Sheldon Browns cassette width measurements and came up with 42mm. I used the original bb as well which puts the chainrings at 50mm.

Obviously 8mm is a big discrepancy, however everything shifts smooth through all gears and the chain doesn't rub in cross chained configurations. With this being the case is it going to cause any problems if I leave it as is, or should I buy a more narrow bb and bring it in a couple mm? Thank you.