If the engine is drawing about 1 oz. of fuel per minute and you go from 4" of fuel tubing to 12" of tubing, It would have about the same affect as lowering the level of the tank about an inch with 4 inches of fuel line. Some engines really don't like a tank that low. That doesn't take into account any other losses other than the length. It might run more like it is 1.5 inches lower once you consider the other losses. I always run a third line and use the least amount of fuel line possible. Yes, static the pressure on both sides is the same as long as the engine isn't running and drawing fuel. Once the fuel starts moving it isn't static any more and there is a pressure loss in the line. The faster the fuel moves, the higher the loss.