Modify
Modify governs success in weapon modification. The Skills & Upgrades guide recommends level 1 or 2 to modify the pistol, shotgun, and laser pistol to level 1, then using French Epstein devices to reach level 2.
How it works
GameBanshee says weapons can be modified a maximum of two times and that French Epstein devices can modify weapons without relying on the skill. It also says Modify can be more useful as a secondary skill in multiplayer because devices per player decrease. The sources offer different recommendations based on play context.
Read the supporting references
Character attributes, technical skills, combat weapon skills, and operating-system upgrades supported by the supplied System Shock 2 reference windows. Guidance explains the referenced mechanics; it is not a tested damage ranking. Check the stated edition and source version before applying a patch-specific detail.