Well I for one am might glad this thread got resurrected as it ended up on my screen yesterday! I've got my first track day next weekend and seeing those initial pictures inspired me to do the same and test out my positioning while stationary on a paddock stand in front of a reflective window this afternoon. Beforehand I thought my body positioning was pretty good, but it turns out that doing this was probably the most useful thing I've ever done! The real valuable moment was when I was in the mid-corner position and tried to take my hand off - I couldn't! My positioning was mostly fine, but I wasn't locked on at all. Turns out I was doing two things very wrong. Firstly, I was too far back in the seat, so only connecting with my knee and not the whole of the inside of my thigh. Secondly, I wasn't using my heels at all. Once I fixed both of these, I could let go of the bars no problem at all. It took quite a long time to instill it in my brain (I'm still a very new rider), but after 20 minutes of imaginary esses on the driveway I began to get a feel for it. It also very quickly became apparent how physically demanding it is to hang on with the lower body and the hands off!
I took the bike out on the road afterwards. It felt wrong to start with (as change usually does), but within an hour I really started to reap the benefits of feeling locked on. If anything, the improvement just highlighted my next problem - looking at the outside of the bend and not my desired line out of it!
I love the fact that I have so much to learn in this sport, every small change is a mini victory! If anyone is unsure about their body positioning, trying it at a standstill is a massively valuable experience so give it a go.