Dutch is right. The way that the tarp attaches to the suspension of a stock HH causes some sag in the tarp when you put weight in the hammock. Even if you don't replace the tarp with something bigger, you'll get a more tight tarp by attaching it directly to the trees instead of those sliding tarp tensioners that came with your HH.
You may actually find that you need to tie the tarp lines to the tree several inches below where you tie your HH spectra. That way, when you get in the hammock and it sags a little, the tarp will still be close to the ridgeline of your bugnet thus offering more protection.
“I think that when the lies are all told and forgot the truth will be there yet. It dont move about from place to place and it dont change from time to time. You cant corrupt it any more than you can salt salt.” - Cormac McCarthy