I had some really tight corners on my cab, and got the molding to go as tight as 1/4" radius! All you have to to is clip the "tongue" of the molding (the part that gets inserted in the groove) 3 or 4 times about 1/4" apart, so it can bend but there's still something left to hold it in place. Pull the molding tight when you're tapping it in. I'd also suggest putting some glue in the slot near the corners, so it stays in place well, especially on inside corners. If your corners are REALLY sharp with no curve at all, cut the molding and butt the two ends together in the corner.
Good luck.