Damage types:
Guristas - Kinetic / Thermal
Serpentis - Thermal / Kinetic
Blood Raider - Thermal / EM
Sansha's Nation - EM / Thermal
Angel Cartel - Kinetic / Explosive / Thermal
Minmatar Fleet - Thermal / Explosive
Amarr Navy - EM / Thermal
Bounty Hunters- EM/ Therm

Main Damage type to shoot at the enemy:
Guristas - Kinetic
Serpentis - Thermal
Mordus - Thermal & Kinetic
Blood - EM & Thermal
Sansha - Thermal
Angel - Explosive
Mercenary - Thermal

Stacking penalty mod for Nth module or rig =
0.5 ^ [ ((N-1) / 2.22292081)^2 ]
1 : 1.0000000000
2 : 0.8691199806
3 : 0.5705831430
4 : 0.2829551534
5 : 0.1059926494
note: modules with highest bonuses are calculated first.