I love mine....marmot I think. Use it when I fly fish the tail water fisheries out west, COLD water . The zipper works for me, just locate the pull in the proper spot Have had it for years, found a really good deal on it...you know one of those hard to sell items. I also added elastic stirrups due to the wader application. A good socking hat does wonders too

I can see that wrap-around zipper being a chafing problem, unless it's really well designed. I'd do a back-yard overnight in it before commuting to a trip with it

Cabelas has similar items. Some Polar fleece, some another synthetic.
This has buttons instead of zippers.

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Price always plays a role, so it pays to shop

Big fan of the onsie here, though mine isn't so high tech, but it does have full arms.  I do prefer buttons to zips, zips near the unprotected tallywacker is worrisome.  Makes for a warm, dry, comfy sleep on the shoulder seasons.  Waistbands suck.

The Big Agnes inflating poly-fill mat is super sweet.

I appreciate the thoughts.  I have been leaning toward the following:

Taking the 30 degree bag, and fastening my blow up Big Agnes air mattress to the inside of my bivvy, which is goretex, with industrial strength velcro .  I think the air beneath me, and a goretex shell below me ought to add 10 degrees or so to my insulation.  Also someone suggested getting a "Man Onesie", which I am considering.  I found this one and I'm not sure I can live without it.    (You need to Login or Register to view media files and links)                                          

About the only time I feel confident a 30 degree bag will do the trick is from about Father's Day to Labor Day.  And even at that, last year you'd have been cold some of the days in between there.

I've taken one trip so far with a Clark Hammock...loved it...and I found little difference in warmth between that and a tent.  One thing that helps is a thermarest of some sort underneath you.  Not only does it help spread the hammock a bit, it also adds a bit of warmth.

Not a serious hanger, but have spent a few nights in my Byer mosquito hammock in a bushwack situation. I use a 20 degree rated bag. But I also have a fleece top and bottoms, that I keep in my bags compression sack. I'll put them in bag with me, and some times I'm glad I did. Nice to have a cozy outfit on for those late night bathroom calls, or to start the morning coffee water stove/fire.

I'd opt for the zero degree bag, unless your the type of person who runs "hot" when the sleep.

You can wear clothes to bed, if you find the 30 degree doesn't keep you warm, but adding clothes is easy in a tent, not so much when your hanging in your bear piñata  Depending on tarp set-up and wind direction, wind will play a big role on whether your warm or cold.

I'd rather have to unzip the bag, than be cold all night. Most bags are generous in there warmth ratings. I'd error on warmer, all things considered

I just got the Clark North American Hammock.  Two years ago was my first Hammock trip.  I loved it, but I was a bit cold.  So, I've read where you can modify hammocks to create more air, or on the Clark, fill the pockets with stuff to make it warmer and that's all fine.  But my question is, what sort of bag rating should I bring in late May or Mid September?  I have a 30 degree bag, and a zero degree bag that both fit into a nice  gore tex bivvy.  I am leaning toward thinking the 30 degree bag should do fine for those dates, but I don't know the answer.  What do you think?