The double_v20.zip file you have requested: Modifications / Single Player / C to D Titles / Double (2.0) - 12mb is not available. Perhaps try browsing all files for the game Doom III and upload any files you want to share or are missing. This is the only information we could locate:
This mod pack contains a set of individual PK4 files, each of them affecting/doubling a specific aspect of the game (weapons accuracy/damage, player's stamina, visual FX etc). If you don't like the features offered by one of them, you just delete it! This mod pack contains a set of individual PK4 files.