We actually have two sit on top kayaks aboard - both are the 9' Wilderness Systems Riot, fantastic plastic - drag them anywhere with no worries about punctures, scrapes or cuts. We lift them over the lifelines to lower them in the water - they're light enough I can get them in the water by myself and even out of the water by myself, although that can be harder.

In this photo, anchored in the Exumas last winter, we have them down on deck getting ready for a storm. If you look closely, you can see the brackets on the stanchions where they normally live. The stainless brackets swing outside the lifelines or inside, so we can swing them out while we're at anchor and in if we don't lash them to the deck underway. Originally we thought we'd always have them lashed to the deck underway, but lately, we leave them in their brackets. In over 11,000 miles of cruising, we've been in some rough seas, but haven't lost them yet, despite naysayers.