Dear Drew,
Thanks for the post and suggested workaround. As I've written elsewhere, we've tried to make SAM's net metering model flexible enough to reasonably model most comment net metering arrangements, but because of the large number of different variations and details, we do not expect to be able to represent all of the variations.
For the next release of SAM planned for the end of this month (June 2015), we are adding options for monthly accounting of excess generation in either dollars or kWh, and an annual minimum charge, so stay tuned for that.
Best regards,
Paul.