Now instead of hanging a full butt cheek off just move somewhere between one to three inches to the side when setting up for the corner... basically very little, see if this lets your outside knee (from the knee to halfway towards the groin) come in contact with the tank more as this is where you will be holding on best (the stronger Quad muscles). If all your contact is close to the groin (abductors) then you wont be able to maintain that pressure for long, best to use the quads which are far more powerful.
Picture that your outside knee can be rivetted into the tank...to get to that position most people need to move a little back in the seat, not so close to the tank, this is where it's important to refine this with a coach in person, as everyone is an individual ("no I'm not!"), now in that position further back from the tank, is it easier to get the upper body lower? can you easily get your knee way further out than before? Does this position give you more room for your arms and potentially for some... the beer gut? Do you feel more stable should you hit bumps? How about how much lighter you can relax on the bars? easier there? Can you last longer at trackdays doing this? with a more stable bike and less lean or more speed with your knee down earlier (big goal for some)? Most importantly or you, how is your footpeg weight? A bit better?
This sounds good but what is this guy doing?
http://www.motorcyclenews.com/upload/212093/images/casey-stoner-practice.jpg