I feel positive I've read somewhere that the armor type mixing penalty only has an effect on maneuvering hinderance, and not stealth, which is solely derived by the armor type and coverage %. Can anyone confirm or deny, with source? Thanks!

While it may not affect “stealth” it will absolutely affect things like slipping of items.

Monster Elec

You hear the distant echo of a savage Horde snarling in barbaric disapproval of your deeds.