I use about .7 to 1 g for blunts, mainly because I only smoke those when I'm with friends (Honestly hate the way wraps smoke. I'm a paper man.).
I usually use the comparison that an average joint is a small blunt, a fat joint is a good blunt, and a cross joint is a fat blunt. (About .4-.5g, .7-1g, and 1.2g, respectively.)

But of course, all this is up to personal preference. :rastasmoke: