I'm sorry to have missed the book club reading of Kosho Uchiyama's Opening the Hand of Thought I'm reading it at the moment and really enjoying it. I've just finished chapter 3 'The Reality of Zazen' and a question has come up that it would be great to get some feedback on. Please read the following quotes from chapter 3:

‘Doing correct Zazen means taking the correct posture and entrusting everything to it.’
‘Doing Zazen is to be full of life aiming at holding a correct zazen posture.’
‘We should be wide awake, aiming at the correct posture with our flesh and bones.’
‘In zazen we have to vividly aim at holding the correct posture yet there is no mark to hit!’
‘Zazen is the best posture for truly aiming at reality as it is. Aiming at this posture of body and life, as it is, is also referred to as shikantaza – just sitting.’
‘Briefly, out attitude in Zazen is aiming at maintaining the posture of Zazen with our flesh and bones, and with our mind letting go of thoughts.’
‘So the essential point when doing zazen is to aim, full of life, at the posture of zazen with our flesh and bones while at the same time leaving everything up to the posture and letting go of thoughts. By aiming at the zazen posture and simultaneously opeing the hand of thought, both body and mind do zazen in the proper spirit.’
‘”Waking up” means to let go of thoughts – that is, we wake up from sleep or thought and perform the reality of the zazen posture that we are practising with our flesh and bones. In other words, it is with our flesh and bones that we actualize the reality of the self.’
‘When we become sleepy during zazen, we have to wake up by vigorously putting our energy into our sitting with our flesh and bones and cease chasing after thoughts.’

My question is: Is Uchiyama recommending that we have our attention on performing the zazen posture, and when we realise we have chased a thought, drop it, and return our attention/awareness to our posture/body? I have been sitting shikantaza without trying to hold my awareness in any particular place... without any object of concentration. I understand that that is the way that folks practice shikantaza around here, and I like it. Trying to hold my awareness in some place seems to me like adding another activity to 'just sitting'. However, today I was sitting and I started to get confused. I wasn't sure whether to be aware of my posture and kind of aim at experiencing it constantly, by way of letting pass any thought that arose in my mind, OR just (as I usually do) let thoughts arise and pass away without interacting with them without having my awareness in any particular place. I starting swinging between the two which disturbed me. Or is it that if we truly let thoughts arise and pass away without engaging with them, we naturally come to be aware of our posture? But then, what of 'dropping body and mind'?!

Are there different views on this within the Soto Zen school? Do some practitioners of shikantaza look to maintain awareness of the posture throughout zazen and return to it, and others not? What did Dogen recommended?

Thank you.