Andy,
Great image.
I have never done that sort of thing, but I have seen incredibly detailed images, traction engines and other parts of the industrial heritage, taken on glass plates.
I like your post title - Don't sell old lenses short. This will set me on a hunt that will be a bit at odds IQ wise with Marks ' Holga ' link.
Might just revisit the pinhole though as I have found some very thin shim material.
Don