What dose constraints would you use for the heart/pericardium when treating a sternal metastasis with five-fraction SBRT?

With the caveat that I would only treat a bone metastasis with SBRT in the setting of oligometastatic disease, I would use the constraints put forward by RTOG in the lung SBRT trials, which is a max dose of 105% (assuming 50Gy in 5) and get lower if possible, especially since there is low likelihood...