I built a cover almost exactly like this on my deck in Seattle, and am having a problem with water dripping down the back (house side). I left the existing gutters in place, and the dripping seems to be a coming from both under the gutters (the bottom) and behind them (a flashing issue?). Any insight would be greatly appreciated. I'm currently considering removing the gutters and allowing the roof to drain onto the plastic cover - but am concerned about the amount of water this would add.