I dont know exactly how much weight it adds but I'd think much more than arrow wraps you can buy. Arrow wraps are the way to go IMO.

And about having white crested arrows in the woods...I wouldn't worry about it. My friend stalked through a creekbed to a bedded deer and got within 20 yds. Deer looked his way, looked back and he took her right there. White crest/fletching and all.