Simulated z = 2.5 galaxy protoclusters shown as projections on the sky plane with thickness 5 h-1 Mpc along the line of sight. Each map is centered on the center-of-mass of progenitor halos that will eventually collapse into z = 0 clusters with (top to bottom) M = [1.1 ́ 1015, 8.8 ́ 1014, 3.1 ́ 1014 h-1M, 1.2 ́ 1014] h-1M. The left-most panel on each row shows the underlying DM distribution (smoothed on 1 h-1 Mpc scales), while the other three panels show tomographic reconstructions from different realizations of mock Lyα forest data with similar sightline separations (ád^ñ = 2.5 h-1 Mpc) and noise as our data. The black contours overplotted on the tomographic maps indicate regions that satisfy our protocluster criterion of dsm < -3 s after smoothing. While this threshold robustly selects massive cluster progenitors with M (z = 0) 3 ́ 1014 h-1M such as on the third row, it is marginal for lower-mass protoclusters as shown on the bottom row. Note that in the second row, the lobe to the upper left ([Dx, Dy] » [-10, 8] h-1 Mpc) will in fact a collapse into a separate, albeit lower mass (M = 1.5 ́ 1014 h-1M) z ~ 0 cluster than the central object.