lots of varialbles,,
would depend on the how clean the stave is,,
and if you would be making it wider with a bend in handle or or just all the same width,,
if you want to be safe,, or conservative,,, or push the limit,,
middle of the road would be like start at say 54,,,
if the bow is not taking any set,, then shorten and retiller,, repeat as needed till you get what you want,,,
but there is not definite answer cause each peace of wood is gonna be different,,
48 is about as short as I would try, there are others that have made shorter,,
the longer the bow the higher the success rate, the shorter the bow the lower the success rate,,
its complicated,,