Duergar - Subrace Stat Modifier Change

[Knight Of Pentacles]

I'd like to suggest that duergar stat modifiers be changed from -4 cha and +2 constitution to just -2 cha singularly. There's really no basis for duergar being any less charismatic than their surface kin and minus four to any stat is a little absurd. It's also said they're less robust than their surface kin which justifies the base constitution score.