The universal carrier paired with the anti-newton ring top glass, I realized is the best option for these machines. The glassless 35mm and 6x6 carrier might seem convenient as you don't have to clean them, but the extra flatness from the glass I found was worth it. It is apparent in the 6x6, less so in the 35mm.

Sometimes the metal universal vanes are not that straight, you can unscrew the bottom and bent them gently.