The drivers seat is mounted, just not sure the fixed passenger seat idea can "work". I can reshape the bottom and backrest to match but the shoulder support and headrest protrude.
The Audi dash shape will match the headrest and the door panels are reshaped as well.
Two seats will have symetry but not at the dash. They will reduce the need for back padding if any but then it will look less "production". This is why I removed the cage and opted for the hidden Engman reinforcements. Making harnesses look "factory" is also a detail challenge...