Ok! Thanks! I was wondering because the image looked terrible without the ground glass! The image is also darker than the factory screen on my Mamiya C330 which seemed wrong for a Beattie screen from what I've read. I went ahead and flipped the fresnel but it didn't make much of a difference.
I also checked with another lens that I have (I would say of mildly dubious reliability) and it reads exactly the same amount off focus as my other lens. I then tried putting a few layers of masking tape on the peg the mirror rests on to lift it just a touch and I get focus at infinity in the middle of the screen, so with the spring removed and the tape on the peg I can hit focus in the middle of the screen.
I have a strong feeling this means the foam under the mirror is degraded and needs to be replaced. I'll take on moderate repairs, but I think that one is a bit beyond my comfort level. I'll use the camera for now for deep depth of field shots, then send it off to a tech to evaluate it once I've beefed up the camera fund a bit.