To address this issue, we reverted our model to a single-frame virtual site approach (Figure ). In this approach beads R1, R2, and C1 defined a single rigid triangular frame, assembled using linear constraints. These beads were also used as the constructing particles from which the remaining beads (other than C2) were defined as out-of-plane virtual sites. Importantly, this single-frame model is not impacted by LINCS convergence issues (Supplementary Figure ). Naturally, time integration stability was a concern: the single-frame virtual site approach had also been explored during the Martini 2 cholesterol development process (using the ROH, R3, and R4 beads), but was ruled out in favor of the dual-frame approach due to instability at multi-microsecond timescales . In our Martini 3 model, the choice of beads for the rigid triangular frame yielded a more stable topology, with no instabilities being observed for 25 × 25 nm 2 membrane bilayers containing 306 cholesterol molecules simulated over 100 μs using a 40 fs timestep. The increased stability of the single-frame model compared to its Martini 2 counterpart is a welcome consequence of the novel focus of Martini 3 in the reproduction of solvent-excluded volumes: particles are now placed closer to the molecular surface than if they were placed at the center of mass of the represented atoms, as was the case with Martini 2. Because of this, the single frame in our model is a much less acute triangle than the single frame in Martini 2, without rotation axes of problematically small moments of inertia.