One-dimesonsional PDFs for all four planets under the assumption that they are coplanar. Inclination and Ω are sampled from 10,000 randomly selected solutions for HR 8799b in our larger Monte Carlo simulation. Assuming coplanarity with HR 8799b leads to eccentricity upper limits of 0.3 for HR 8799c and d, and 0.5 for HR 8799e. The reduced χ² for these fits for HR 8799c, d, and e are small, showing that coplanarity is completely consistent with our data. Also, as in Figure 9, we note the locations of 1:2:4:8 period ratios assuming the distribution for HR 8799e is the start of the chain. All four planets align very well with these period ratios.