SXR based or not, the lighter the hull the less it'll stick to the water and carve. Sounds like you want to stick with an SXR based hull but lose some weight for extra versatility. Just realize that the lighter and shorter you go the more you take away from the carving race hull feel. Aquabot and Backie Chan are deep chined SXR style bottom decked hulls that are very playful yet can really dig and rail turns. I'm no flatwater guy but I'm loving the Aquabot in surf and I'm amazed how well it rides and handles for being a smaller hull. Heavier surf layup helps.