The taut line is used in my climbing gear rope for 1/2 inch arbor plex rope. It holds me securely enought that i can limb walk over power lines without it slipping.when you tie your knot use four wraps instead of three,only make the last wrap in the opposite direction of the other three. This give the knot a space between the last two wraps. This acts like a knot with an anchor knot behind it. Im not sure, but ive been told that this resembles a mid shipmans knot ,but i dont know for sure of the exact configuration of the mid shipmans.This method puts a sharper twist to the knot making it hold tighter.I dont feel you will have a problem with it holding. Good luck.
PS. If you chose to try something different , put the suspension cordage through the eye of the tree hugger twice instead of once ,the half hitch that would develop in the eye would definatly hold tighter ,then you would not need the marlin spike. It also could alow you to shorten up on the tree hugger length a little. You would have to pull the weight of the hammock off the line to adjust it though.
Splicing does not reduce the strength of the cordage as bad as a knots does.