From the Cloudy Nights thread it does sound like the Head Rest helps at 10x with comments by Erik Baker and responding to a question from Anders Asp. Impressive that he says the Head Rest closed the gap between the Canon IS 10x42 in stability by 3/4 but the NL had much better image quality.
"Last night I observed for the first time with my newly arrived FRP forehead rest with my NL 10x42 and what a difference that makes! Both observing standing and lying in a comfortable reclining chair, it closely resembled the stability of using a tripod, but without the hassle, with only a small loss in stability. And what a joy to take in these stable, high-quality images. A very simple but highly effective accessory for improving hand-held observing with the NL's."
"Erik, do you by any chance have the possibility to compare any Canon 10x42 IS binos with your Swarovski 10x42 NL Pure with FRP to see how well the Swarovski handles shakes and who of the two binos delivers the most pleasant views?
I'm thinking about maybe going for the 10x42 or 12x42 with an FRP if the support device really works in such a good way as people say and it really can deliver more or less the same stable views as an IS binocular."
Anders Asp
"No, I have not compared them, but did so with the EL 10x42. The EL had a nicer crisper view, but with more shake. Now with the FRP the gap in shake is about halfway to 3/4 closed, depending on how you use them and how high in the sky you observe. Image quality in the NL is better than the EL and much better than the Canon IS 10x42. Of the 10x and 12x NL models, the 10x is better, whereas the 12x is stretching the optics a bit far."