Good question Pen s. & Oren Grad

I have a Horseman VH which is a folding medium format which has limited movements, has a ground glass (or reflex viewer which is fantastic) and takes large format type shutter/lenses.
So, I think the camera should work quite well with the Holga lens. The coverage will be fine (same format as Holga) and the focal length of 60mm will be fine. My only concern is the whether the aperture of the Polaroid Copal shutter (00 I believe) will be wide enough and not cause vignetting?

Jon, thanks for your practical suggestion. I will definately rig up something with cardboard to try this out first, before sinking money into a threaded adapter and retaining ring. I did hear back from S. K. Grimes and the price for said item would be about $130 (as it's custom).

My thought at this point is to drill a hole through a thin piece of wood or plexi slightly smaller than the diameter of the meniscus. Then mount the lens over the hole with tape or glue and then mount (tape) the substrate over the backside of lens behind the shutter, attempting to have the lens as far inside the shutter barrel as possible (as it's 20 cm deep) to avoid vignetting.
For those who have not seen it, the Hola lens is only 22.5 mm in diameter. it's quite small. The diameter of the shutter is aprox. 25mm wide open.

Perhaps if this works well enough, I might invest later in the threaded adapter.

Thanks all for your suggestions.