Radial extent of H I and CO in NGC 1566, NGC 1672, and NGC 3511. These galaxies have the largest H I disk extent in our sample, and exhibit special H I characteristics. We indicate R_eff, r₂₅ and R_HI as grey, pink, and orange vertical dashed lines, respectively (taken from Table 1). Top: we note here two additional clumps outside of NGC 1566’s main H I disk that have been identified as additional field galaxies (see de Blok et al. 2024). Middle: toward NGC 1672 we see an increase of H I emission at r_gal ∼ 70 kpc, which is the region of additional low-H I emission in the west of NGC 1672’s disk (see also Figure 3). Bottom: The hatched region from r_gal = 40-120 kpc spans the low-density filamentary structure seen in the moment map (see Figure 3), which gives the impression of connecting NGC 3511 and NGC 3513.