I just saw this, so I guess I'm a bit late to the party..

Anyway I use a 16T JT front sprocket (the bike is an XL600V) for a while now and it doesn't need any modification as it stays clear of the casing. I went back on a 15T after a major service when I wanted some more bang to feel the difference and changed it back a week later. The bike suddenly felt so stressed above 60 (100kms) compared to the 16T. It has to be said that when riding two-up in urban rides, or on moderately rough off-road, I miss the 15T but on every other case I believe the 16T is the winner.