Originally Posted by John Snyder
I am one of the persons involved in the production of S&S film holders. It is hard to address some of your questions without actually seing the holders. However, a few comments.
1. There is no standard in terms of a "given/accepted dimension for the gap in the channel the film loads." Reasonably, it should be as tight as possible while still allowing the film to load. On our holders this gap is approximately 1mm. I would consider a gap of 2mm too large, but whether such a gap would affect sharpness depends on what type of photograhy you do. If close up using wide apertures, it might. At normal landscape distances using f/32 and smaller apertures it would not. Sagging will not normally be a problem unless you tilt the back backward away from vertical.
2. Since you are not satisfied with the holders, I belive you have a right to return them. As a seller I would definitely refund your money rather than risk negative feedback. This would be especially true if the original advertisement in ebay advertised the holders as" film holders" rather thann plate holders converted for use with film. Or for that matter, if it only stated holders without specifiying plate holders converted for film. Some, and I am one of them, would consider that wording "deceptive advertising."