Blueslide,

I can tell you about a simple rig to keep the water from collecting on your tarp. First of all do spend the money to get the heavy duty silver tarp with the black backing. All plastics will degrade over time in the sun, but the silver is reflective as well as thicker. While you are at the Home Depot buying the tarp, go to the lumber dept and pick up a 16' 2x6. this will become your center stay , running from your bow to the stern. Depending on the actual measurement you may have to trim the stay, with a point on one end and notches made for stowage or seats. The ones I have seen fit fairly snug. Once you are sure the 2x6 will stay there, then use bungies or ropes to tighten the tarp. Good luck

Paul