If the zipper was too tight to close easily, it was definitely too tight. As Passinthrough suggests, I also use the visual droop of the storm shield to judge the tightness, but I don't let it droop quite that much. Have you looked at the video describing the NX-250 on the Clark website? It gives a very good visual of the proper (at least for me) droop of the storm shield and tilt of the spreader rods. Experiment with the proper amount of droop for you, note what the storm shield looks like, and is surprisingly easy to set it up the same again.
If it is too tight for the zipper to close properly, it also seems to add the hard ridge lines to the middle of the hammock where your legs are. For me, it is also important to get the foot end a little higher than the head. Passinthrough's suggestion for setting this using the position of the low part of the droop is something I hadn't thought of and I can't wait to try. It makes a lot of sense.
Love your enemies, but keep your gun oiled!
I am a CONCENTRATED vegetarian. I let the cows eat all the grass, and then I eat the cows!