If you think that 53/16 is your most desirable gearing combination for flats, I suspect your cadence is on the low side. At a very attainable and highly desirable 95/min that would be about 25 mi/hr. Hardly all purpose. I suspect your cadence is much lower, around 70-80/min or so. Easiest solution to your problem is to increase your cadence and use a larger rear cog. Even a small increase would allow you to use the readily available 17 tooth cog.