Keep in mind that the geometry of the hammock will play a large role in the forces that the ropes will need to hold. The tension goes up with 1/sin of the angle. So as the hammock gets straighter, the tension goes up a lot.

For example, if the ropes are straight up and down (like a swing) then each one takes 50% your weight. If the angle of the rope to the horizontal is 45 deg then each rope takes 70%, at 30 deg each rope takes 100% weight. At 20 deg it's 150% and at 10 deg it's 300%~! If the angle is zero, in theory the tension is infinite.

So it may not be a good idea to tension the hammock support ropes too much with an inline knot. Remember this is your life you're supporting. I read about a guy who died when his friend jumped on him in a hammock, the rope at the head end broke and he landed on his head, breaking his neck.