I'm trying to think back to the first couple of nights in the Hennessy - I didn't have anywhere at the apartment to hang it, and didn't think about local parks, so went on a 10 mile hike in the wrong shoes and nearly froze myself changing clothes... I had a blue ccf and a Ray Way quilt, and the temps dropped significantly to the point that I had cold spots. But I slept, maybe because I was exhausted and footsore. Didn't really have a problem after that.
But, after using the HH for a few trips, I started to feel claustrophobic... so here I am with a Blackbird. I'm just puzzled that anyone would find it constricting, I'm definitely sensitive to constricting places. I even sleep on my right side and I'd think that would put my face in the sidewall but I can't recall that being a problem.