I would try a combination of lower peak weight and less letoff. A little higher holding weight lends itself to more stability at full draw. With a high letoff bow there is often not enough holding weight to overcome the weight of the bow so you have to physically hold the bow up which tires out the bow arm. Another way to accomplish this is, if you have a solid back wall, to shorten the draw slightly so that you pull into the wall a little harder, thus making you use more back muscles instead of arm and shoulders to shoot the bow.