Mechanically, the Stages Power left-side power meters are 100% compatible for use with Osymetric, Q-Ring, Absoluteblack, and other non-round chain rings.
Power measurement through a Stages Power meter is event based, where as an event is one complete pedal revolution. Due to the changes in velocity non-round chain rings produce through the course of an 'event', you will see that your power will be skewed higher than with a round ring, which has a constant velocity throughout each event. Through our own testing, and using a hub-based meter as a control, we conclude that there will be a 4-5% increase on the readings from a Stages Power meter when used with a non-round chain rings. The difference between the readings will depend on the ovality of the chainring you are using. We recommend that our customers take this into account when changing from round to non-round chain rings, as they may need to adjust their functional threshold power accordingly.