As Ian said this will result in quite a magnification. There is a close up calculator on hasselbladhistorical.eu where you can find out in how wide a field of view these combinations will result. Hasselblad did also offer a chart for download but I can´t find the link anymore. Just write me a pm if you´re interested.
One person you might wish to PM is PentaxPete
(there was a url link here which no longer exists)
It seems to work well for him. I tried a tube on a 35 last week & would like to find some for the 'blad also. My only gripe w/ the 80mm is the 3' min. focus distance. That's one reason I bought the 50mm, which I use most.
As Ian said this will result in quite a magnification. There is a close up calculator on hasselbladhistorical.eu where you can find out in how wide a field of view these combinations will result. Hasselblad did also offer a chart for download but I can´t find the link anymore. Just write me a pm if you´re interested.