It is a total gamble really.

If you try it there is a risk (high by the sounds of it) that approaching the day F will be closed and anyone there will be shunted back to J. At that stage there may only be centre seats left, you will feel a bit irked but the chorus on here will be "well you got what you paid for".

Then again it may re-open but you will be unable to get an F seat as they will have been allocated in a way that we may never understand (for example to BA staffers and the like). At which point the tune here will change to "it isn't any of your business who was sat there, you still got what you paid for".

As I say, all a gamble, better to select a seat you are happy with and leave it at that.