Two options in this remix: (1) use modified bases which will fit better on the bottom of the sterilite boxes OR (2) print spacers for existing 100% printable filament spool holder bases.

Option 1: Use the Base_Sterilite20qt.stl instead of motoz version to fit Sterilite 20qt weatherproof box

Option 2: Retrofit bases you have already printed with the spacers, they friction fit on snugly. You will need to print 2x of both Spacer(A) and Spacer(B). For added security, add a dab of cyanoacrylate glue before sticking the spacers on.