How to initialize a WASAPI with as low latency as possible?

How can I initialize a WASAPI audio device with as low latency as possible. Right now I'm using AudioCategory_ForegroundOnlyMedia and AUDCLNT_STREAMFLAGS_EVENTCALLBACK, AUDCLNT_STREAMFLAGS_NOPERSIST as flags. Is there anything more I can do to lower the buffer size?

The application is a syntheziser, it generates audio on the fly.

(As this application is intended to run on Windows phone I'm constrained to AUDCLNT_SHAREMODE_SHARED and HWOffload = false)