Wista Folding Monocular Reflex Viewer Anyone?

I have a Wista 45SP and have been considering purchasing the monocular hood for years. It's very pricey though. I was wondering if anyone has this and what experience they can give. Does it replace a dark cloth? Is it bright enough to use for critical viewing? I would really enjoy the upright and reversed view.

I had a Wista DXII with the reflex viewer. It is very bright, it has an internal fresnel. However, I prefer to look at the GG reversed image. I bought that camera second hand with the reflex viewer and some other accessories. I would never buy that viewer, it's too expensive. It gives you an upright image, if you use horizontal composition but, in vertical position, you will see a reversed image.