The fn × Q (Hz) is a crucial sensitivity parameter for micro-electro-mechanical sensing. We have recently shown a fn × Q product of ∼1012 Hz for microstrings made of cubic siliconcarbide on silicon, establishing a new state-of-the-art and opening new frontiers for mass sensing applications. In this work, we analyse the main parameters influencing the frequency and quality factor of siliconcarbide microstrings (material properties, microstring geometry, clamping condition, and environmental pressure) and investigate the potential for approaching the theoretical upper limit. We indicate that our previous result is only about a factor 2 lower than the thermoelastic dissipation limit. For fully reaching this upper limit, a substantial reduction of the defects in the siliconcarbide thin film would be required, while maintaining a high residual tensile stress in the perfect-clamped strings.