*all images may include upgraded options* 20’4″x66″ sled starting at $29,995.00! including 115 evinrude e-tec pump and tille. our 20′ 4″ flat bottom sled is. Specmar aluminum catamaran hulls are either symmetrical or asymmetrical in design. a symmetrical hull consists of two basic v-bottom hull structures.. It takes only a little time, money, and effort to build one of these rugged – yet simple – flat bottom skiffs. every model includes details for two bottom profile shapes..