No minimum draw length. At some point in the draw of the bow before or up to 28" it must take 40lbs of pull to draw it. As long as in that first 28" you hit 40lbs at some point you are legal. If at 22" you hit 40lbs and then at 24" it breaks over to the 65% letoff and you are now at less than 30lbs you are still good because it hit 40lbs in the draw cycle.
There is a rule about arrow length and the arrow has to be 20", so if you have a super short draw your arrow has to be at least 20" long.
If you are shooting a 40lb bow and really short arrows you then also have to worry about arrow wait and be at least 300 grains arrow, nock, broadhead and fletches combined total weight. (The 6 grains per pound doesn't apply to a bow with only 40lbs of pull because it is then under the 300 grain minimum.)
