Morningstar does not recommend using 60 cell modules for charging a battery system with a PWM controller.
There are a couple of issues with attempting to use 60 Cell modules with a PWM Controller. First, a 60 Cell module will typically have a Voc of ~36 and a VMP of ~30 at STC of 25C. Many Morningstar PWM Controllers have a Maximum voltage input rating of 30V when used in a 12V battery configuration, and 60V when used with a 24V battery configuration. The input voltage from a 60 cell module will exceed the 30V rating for PWM controllers when used in a 12V config, and if 2 panels are put in series will exceed the 60V rating for a 24V system resulting in a damaged controller.
For charging a 12V battery with a PWM Controller, a 36 Cell Panel is recommended.  For charging a 24V battery, either a 72 Cell Panel or (2) 36cell panels in series is recommended