As you mentioned, I installed the BB from the drive side and tightened fully using a torque wrench. Then I installed the opposite side. The FD does not touch the chain rings at all. I removed the cable to the FD, unscrewed the high limit stop screw, and pulled on the FD to see how far it would go. It reaches but does not clear the outer ring. Frankly, if the chain line were 50 mm rather than 51.5 mm, I'm not sure the extra 1.5 mm would get the FD to clear the large ring enough for the chain to operate at all or effectively. I'm wondering whether the Suntour FD-XR15 derailleur is for a 47.5 mm chain line? I could not find any specs on it.