What I think we are going to do, after talking to a number of different guys and a couple vets, is long term antibiotics. 30 day cycles. It should wall the cheatgrass in scar tissue over time and sterilize it, if it doesn't work itself out. We can still hunt him on this treatment method.
We don't think the cheatgrass is going towards a vital organ at this time. That would be a different scenario. The surgery is expensive, probably have to remove a rib, not a high success rate plus a long recovery time and very painful.