When treating resected brain metastases with post-op SRS, what dose, fractionation and PTV margin do you use for large (>3 cm) cavities?

Two randomized trials which included single-fraction post-op SRS as an arm reported high 1-year local failure. In Alliance N107C (12-20 Gy, 2 mm PTV margin) and an MDACC trial (12-16 Gy, 1 mm PTV margin), 1 year local failure rates were 44% and 28%, respectively. Even higher risk of local failure might be expected in the subset with >3 cm cavities, since tumor size correlated with recurrence (and also lower SRS dose). For intact brain mets, a large retrospective (Minitti et al, IJROBP 2016) comparison of 15-16 Gy x1 vs 9 Gy x3 using 1-2 mm PTV margins for mets >3 cm found that hypofractionated therapy significantly reduced local failure (46% vs 27%, p = 0.02). Should this approach be adopted in the post-op setting?