The second phase of the LEAP project investigating the liquefaction of a 5◦ saturated sand slope has commenced, focused on the effects of relative density and input motion. Thus, reliably estimating the density and quantifying the associated uncertainty is cardinal. The sensitivity of the calculated relative density to small measurement errors on the sand mass and volume during model preparation is highlighted. Settlement during swing-up, quantified using particle image velocimetry, implies a small densification of the soil mass. Recognition of the stress dependent soil stiffness is required to model the measured settlement profile. Finally, in-flight miniature CPT tests are discussed for further analysis of density. Empirical correlations linking cone resistance to relative density appear to agree with measurements from the pouring stage.However, the dependence of cone resistance on other factors like the lateral stress state requires further investigation. Overall, the CPT provides instructive insights into key model properties.