I've tried the hammock with a Ridgerest and BA Insulated Air Core Rectangular - both 20" x 72". Haven't tried it without a pad yet. While I'm at the upper end of the weight limit, in men's sizes I wear a Large shirt (a little big on the shoulders) and an XLarge pant (lotta junk in the trunk ). I didn't have any trouble with squeeze at all - it was a bit narrow at the hips when I turned over on my side. Once turned, I was able to bring the upper leg up from hip to knee at about a 30 - 40* angle which is my normal sleeping position.
As for side insulation - I would likely add some SPE to the edge of my underquilt so they would be on the outside if I found I needed them and use the BlackBishop skin that is like a bag to store both the underquilt w/ SPE and hammock. I do not normally sleep out in really cold temps because getting cold makes my bad leg ache. I will be doing some of this close to home to test this hammock, however. I'm waiting until I get over whatever nasty virus or infection I've had to do this - I started my third round of antibiotics today and am already feeling better.
I'll see if I can get He-Dino to crawl in the hammock and see if he gets squeezed - He's 6' and about 200lbs.