[JesseK]

Most polycord has a minimum pulley diameter, and the pulley diameter gets bigger as the cord diameter gets bigger. Exceeding the minimum diameter puts extra load on the motor driving it.

For example, the hollow Yellow Round Urethane belts my team likes to use (McMaster # 6567K56) has a minimum pulley diameter of 1.5". This year we were able to get away with a 1" diameter @ 3% cord stretch, given the gearing & power of the motors we chose. If we used a weaker motor or faster gearing, we would have probably enforced the 1.5" diameter design parameter. We also relaxed the belts overnight and in between competition so they didn't wear faster than expected.

Just something to keep in mind.