Here's a clue: A pair of Stealth Centreboards weighed 3.4kgs. New VWM Blade (Hans) 3.6kgs. Auz Blade 4.2kgs and the Vipers were a little over 8kgs. Realistically a good weight for Cb's is around 2kg especially given the conditions at Zandvoort. Attached is a photo of the Auz Blades boards and rudders