I have experienced a similar "balancing-on-a-pinhead" feeling that Wingswinger cites. The only difference is that it was in a glider so I'm wondering if canopy shape in relation to pilot position and/or sortie type have anything to do with it?
I was just thinking something similar when I read your post. It would be interesting to know if some helicopter pilots get it?
I flew gliders for a few years and felt this odd out of body like experience on a few occasions. It only lasted a few seconds and was quite enjoyable usually. To me it felt like I was out in front of the plane. Never noticed it when I was busy. Once or twice the sensation was uncomfortable - a bit like discovering everything has gone quiet because you are close to stalling.