Accurate structural weight prediction for novel vehicle configurations is an important and often neglected aspect of conceptual design. Many unconventional vehicle concepts are not well represented by empirical structural weight models based on historical data. Traditional finite element modeling and sizing optimization is a time-consuming man-in-the-loop process. This paper describes the process of bringing the accuracy of finite element modeling and physics-based loads modeling to the conceptual design stage in a streamlined workflow for rapid structural weight prediction. M4 Structures Studio (M4SS), a tool to parametrically define the structural configuration for aircraft and quickly estimate structural weight, has been enhanced to support the modeling of rotorcraft structures. Preliminary sizing results are presented for a NASA Urban Air Mobility concept [1].