Ignoring the weight of the rubber itself (way more than 3 oz I'd say) and the hysteresis loss (energy lost from the system as heat during the stretching-contraction of the rubber), which would be the same regardless of the size of shot bag used, the mass of the 3 oz bag + half of the fishing line between you and the branch would probably be less than half of the mass of the 8 oz bag plus half of the nylon throwline I use.

Therefore as potential energy gained = mass x g x height, then the height would be more than twice 130ft. So 280ft would be possible. However the rubber IS a big factor. Another big factor is the increased air resistance-to-mass ratio of the smaller bag, (which is also travelling at a higher average velocity as it needs to reach a greater height) - think of how fast a human free-falls compared with how fast an ant free-falls - smaller _object_s of similar shape and density slow down faster in the air.

Right, that's enough high school physics. Sorry for the digression

Michael