Admin note: the main WAD here works in vanilla, but fails in source ports due to the error:
  P_LoadSegs: linedef 809 for seg 599 references a non-existent sidedef 65535

This was fixed by manually adding the necessary sector and sidedef entries to the WAD lumps and modifying the LINEDEFS lump to reference those sidedefs in Slade, along with a padding REJECT lump with null bytes. The initial fix was by 4shockblast and the padding was done by Keyboard_Doomer.