First I used the Panagor extension tube set (11mm, 18mm + 36mm) in combination with the Porst 2.8/55mm lens at the Porst reflex TL. It's a typical heavy and simple, but cool 1970s SLR made by Cosina. I bought it very cheap at Ebay.
The performance of the extension tubes are very good, but I wanted a little bit more, therefore I attached Hama Macro Lens +10 to the setup. The enlarging factor is really hot!