The true Minox enlarger takes care of all of these factors in its own unique way. When using another enlarger, operation is likely to be some sort of compromise. The Minolta 16mm enlarger is just such for it is capable of handling several formats with varying amounts of trade off. The 16mm negative carrier is a straightforward design and is essentially a slightly scaled down version of what one might find in a conventional 35mm enlarger.
When I was using mine for half frame work, I duplicated the design with the refinement of providing an offset so that only the perforated edges were in contact with the carrier, to minimise risk of scratching.
However, I found that this didn't hold the film flat enough and perfect focus over the whole frame couldn't always be obtained. In the end, I returned to a simpler design (shown below) of two hinged plates which are pressed together when the assembly is inserted into the enlarger. The folded flanges around the edges are to ensure accurate location in the enlarger and to minimise light leaks from around the carrier which could otherwise fog materials exposed in the darkroom, as well as give some dimensional stability. The tab on the upper face is to allow lifting when the negative needs to be moved.
The 8x11mm hole was cut after the upper and lower plates had been hinged together in order to ensure accurate registration. The plates themselves are made from 0.1mm brass shim obtained from a local hobby shop.
Guide pins are desirable to locate the film in the carrier and to guarantee accurate location of the plates when the carrier is closed. The easiest way to fit the pins is to use a discarded piece of minox film which is taped in correct position. The edges are marked with a fine scribe after which holes (0.5mm) are drilled right through both upper and lower plates just clear of the edges (leave a little leeway to provide for varying film width). Brass wire is then passed through and soldered into place on the bottom plate. The wires are then cut back with snips and the ends polished with fine emery to prevent scratching.
To finish the whole, it's given a polish with more emery paper, washed & dried, after which all external faces can be painted matt black with automobile spray paint. Whilst this design is specific for my Minolta enlarger, similar carriers could be made for others in quite analogous ways. It doesn't take much in the way of tools - a hacksaw, files, small vice and drill. I hope this may give others some helpful inspiration !
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