You really only have the SC reading and those two yacht club ones to make your choice from. Other than that ring the the crew at Peninsular Kiteboarding, they are only opposite the grassed area at Rosebud and just about see the water from the front counter, should be able to give you a good up date.
Im a firm believer that you take 5 knots from the SC marker reading. According to the BOM the gauge is approx 15m above sea leave

and the winds always seem to be stronger up higher.