There's a lot of factors that come into play, such as style of bow, width of limb, wood choice and the intended use of the bow. Adding deflex to the handle allows you to make a shorter bow, how short depends on how much deflex. More limb width, which gives you more working wood, allows you to make a bow shorter as well and using a more elastic wood does the same thing. If you want a target bow as opposed to a strictly hunting bow then you must make it longer for it to last longer.