How long would the staff of a composite bow be for a 28" draw?

I am trying to, as a gift to my Father, design a composite bow of Mongol/Scythian/Turkish Origin. Although, I was hoping to make the bow a little taller in height, with a draw of somewhere between 28” to 30”. I am rather new at bow-making, and I know this one will take a while to make, so I want to make sure I have the length right before I even begin.