Note: you use ChassisDef to create new chassis of a 'mech, i.e. a 'mech blueprint with completely new hardpoints.
You use MechDef to create new variant of existing chassis, i.e. you swap weapons within existing hardpoints.
There is other implication: if you kill a 'mech, it will drop salvage parts based on chassis it uses.
@Max_Killjoy : I also just started with the mods, so we are in the same boat - trying to figure out what's what to have extra things included in the game.
You use MechDef to create new variant of existing chassis, i.e. you swap weapons within existing hardpoints.
There is other implication: if you kill a 'mech, it will drop salvage parts based on chassis it uses.
@Max_Killjoy : I also just started with the mods, so we are in the same boat - trying to figure out what's what to have extra things included in the game.