I am a bit of a novice kayaker -- basically a triathlete who does some adventure racing with kayak portions of about 12 miles, smooth river water but sometimes shallow and with rocks. I am currently paddling a Necky 13 but want something faster. I'm concerned about getting a composite design due to bouncing off rocks occasionally. Would the people on your forum suggest a Necky Cjatham 17 or a Wilderness Systems Tempest 170. Both are 17 feet and both are about the same in price. I am about 5'11" and 165 lbs.