Reversing the lens orientation is common practice in macro photography. To get even more magnification you can increase the distance between the film and lens by using an extension tube or bellows. [Kevin] built this variable length extension tube by modifying a bunch of cheap used filters. When I say “modify” I mean he “broke the glass out with a hammer”. The base of the extension tube is a body cap that has had the center removed. Glued on top of body cap is a filter ring with the male threads pointing forward to act as the reverse lens mount. You can add any number of additional rings to change the length. It’s very important to be thorough when cleaning your filter rings otherwise you might damage your camera internals.