I have never had any problems loading a conventional 35mm camera, always using the "reverse" method, nor have I had any problems with bottom-loading FSU cameras or my M3. BUT, the Horizon panoramic camera is in a league of its own. You have to insert the cassette with the film slot downwards and away from you, thread the leader under a roller, across the top of the curved "gate", then under another roller and under the take-up spool at the same time, then extract the leader from the back wall behind the take-up spool to feed it into the slot in the take-up spool. I have found it slightly easier to fold the first 1/2" of the leader backwards and then use tweezers to feed it into the take-up spool slot.