My single glider is optimised for the lightest pilot in our syndicate by having lead weights (factory) fitted inside the tail wheel so as to reduce drag at normal cruise. In addition it has a water tank in the fin that allows us to add up to 8 litres of water in 1 litre increments. One has to do weight and balance calculations carefully. Spins well. Needs correct recovery. (It also has water ballast tanks in the wings with a total capacity of 200 litres.)