I would say we have at least 30% more hull volume than the Viper. The Viper is a fantastic, well built boat and the benchmark for all F16's, but we chose not to go lighter as we feel the 125kg-130kg range is optimum on the schrs handicap rating system we use in the UK. look at the Falcons, originally they were under 120kg now they have crept up to the 125kg-130kg range.