the h17 is designed for singlehanding and rates faster than a h16 sailed 2 up. the 16 is a powerful handful as a singlehander and is probably just as fast as a 17. the 18 is faster. period. a bigger faster more powerful boat. theres a guy at our club who singlehands his and he's not real big, maybe 5'9 and 185lbs. he's also an experienced risk taker (hang gliding, gyrocopters, kite sailing, etc) so he knows about limits. if it were me i'd rebuild the 16, sounds like the pieces are available and you'd probably come out cheaper.