The 28 day rule is applied to protect the individuals gratuity payment - I recall from tax! THat is how it worked when I went from Regular to FTRS
If you are doing changes to your establishment then you have the benefit of the AIR RF Manning Team at HW. Dont rely on individual input as we all have different intrepetations. FTRS as you know has lots of different issues notwthstanding FC/LC/HC/ADC etc