I fired a clip (18) of normal elites, then a clip of the suction tips (done multiple times for a good test group). They curve off still, but around a 5 foot spread (approx.), whereas the normal elites were closer to a 15-20 foot spread. All tests were fired out of my angel breached longshot from my shoulder at eyeballed level. I have measured my basement before, and it's 55 feet from end to end, and once i'm standing there the tip of thee barrel is roughly 50 feet from the opposite wall.
The darts are not much heavier than normal elites, barely noticeable when comparing one in each hand. I do not have an accurate scale to verify this though (I might soon). The main bulk of the tip (under the suction tip) is shorter than a normal elite tip, but its a solid chunk of rubber. Id expect it has a larger mass of rubber than normal ones.
The felt pad weighs less than hotglue, so they're a little lighter than cutting off the tip of a normal elite, dropping a bb in, and hotglueing over. But they still weigh a decent amount more than the unmodified ones, and more than an unmodified elite.
Griever- I have been purchasing them in 30 packs at my local walmart. They've kept them pretty well stocked too.

EDIT: Here's a picture of the heads of a suction tip dart and a zombiestrike elite. The regular elite heads have a more plastic-ish nub that goes down into the foam, whereas the suction tips are all rubber. I personally think the rubber would be heavier than the plastic to begin with, plus they are longer, leading me to believe they are heavier.
Edited by Azrael0987, 27 March 2014 - 10:44 AM.