I have a fixed gear bike with a number of cogs. I have a 3/32 eight speed chain which allows lateral flex. One of the cogs is a dual cog and works with the chain as there is sufficient lateral flex but the chain line is obviously not straight. No indication of the chain binding due to being off a straight line. I ride long road rides, 50-80 miles, sometimes with geared riders. Is the dual cog not a good idea if I'm trying to ride as efficiently as I can? I took off the dual over concerns it may not be as efficient as a single cog. The advantage of the dual cog is I can switch between 70 and 80 inches without removing the wheel. I have a flat Thursday ride I can use the 80". It's not a big deal to take off the wheel and change the cog if it is better to run a single cog with a straight chain line. thanks