conventional wisdom says that max draw will be equal to 1/2 the total working limb, so 23 inches for you. If you shorten the non-bending grip or any stiff tips, you'll get more. If you make it wide, you'll get more. With excellent tiller and excellent wood you will get more. So, unless you are quite short, you will probably want to shorten the non bending sections- 66 should be plenty long to get to 28 inch draw if you do it right.