Tom, essentially the deck limit mark can be placed where you want is my take. I would imagine any limit mark would need to be placed in a position that can be visually identified and relevent points checked for compliance against on inspection. I.e. could i readily check that the upper edge of your lower mast band point is within the required 60mm min and 100mm maximum range allowed?
Before getting too far ahead, worth understanding the class rules what is mandatory regarding fittings, especially the kicker. You may find you need a mast well of some sort to allow for a kicking strap that meets the rules.
The recommended notion that anyone trying anything new should ask for an interpretation from firstly their local measurer who if not clear will pass upwards to a National Technical Officer, then oneards to the International Technical Officer is a correct one. When we can expect that all will follow this advise instead of circumvention or that the playing field will become level for all designers, builders or manufacturers is anyones guess…