Half-light radii of CO(1–0) and [C II] emission vs. star formation rate (left) and total molecular gas mass (right) for galaxies from our sample and from the literature (see Section 4.1 for references). The protoclusters from Emonts et al. (2016) and Dannerbauer et al. (2017) are highlighted by circles, and open symbols indicate lensed sources from Stanley et al. (2023). We also show predictions for z = 3.1 galaxies from the SIMBA simulation (Davé et al. 2019) as open grey symbols, and the grey lines indicate the running average. The inferred size of the CO(1–0) emission in our sample is consistent with the extended CO(1–0) and [C II] reservoirs around other high-redshift DSFGs with a comparable SFR.