Print spec reporter output to file in WebdriverIO?

I'm trying to find a way to print spec reporter output to a text file once the test suite is complete. I'm using WebdriverIO but none of the completion callbacks seem to provide any access to the actual report output. There's also no documentation on any config variable you can pass in to set a file output. There an outputDir option but it only writes the log before the actual report to the selected location.