What SBRT dose and constraints would you use for a primary endobronchial NSCLC that is too thick for brachytherapy?  

It really depends on the size and location of the lesion with respect to the proximal bronchial tree and other mediastinal structures (such as the esophagus). SBRT, as commonly understood (e.g., 50 Gy in 5 fractions), strikes me as risky in most such scenarios. Something more like 60 Gy in 15 fracti...