My ironman idiot wanted to do a steady 18mph, and went slow uphill to keep his heart rate down so that wasn't a problem. FG downhill can be a problem with a fast geared bike, but SS isn't a problem as I just draft tight. Cogs are not too expensive - it might have been cheaper to do a 42x15 than a 46x16, practically the same gear.

Enjoy the Langster!