The collapsible nature of the fabric Darksleeve is the only thing that allows film of this size to be loaded in a tent at all. Standard film holders double in size when you need to withdraw the dark slide completely.
I've made some sets of film holders, 7x17, 11x14, 11x17, and 8x10. I have some 20x24 film I need to cut down; the most economical way to use that will be 10x12, so I need to make some of those too.
These holders are prototypes, designed to do little more than test and prove the concept, and there is still some more work to be done. Rather than use a universal template for all sizes, it seems that each size will need a custom design, regarding the placement of the magnetic clips and registration pins.
Going forward, the next set of film holders will be far lighter, unfortunately, that can only be achieved through the use of expensive composite materials, and a more complex manufacturing process.
The film is loaded in very much the same way as a standard holder- the film is slipped between slots on three sides, and the fourth side is gripped by a magnetically attached clip, rather than a hinged flap.
The film holder is contained within a fabric sleeve, as mentioned elsewhere, which is made up of two layers of lightweight blackout fabric. Used in a single layer, this fabric is not 100% opaque, adding the second layer is vital. It is not yet known how much the addition of the second layer attenuates the transmission of light, I suppose I could test for it by leaving a loaded film holder exposed to bright sunlight, using a test strip system. But I'll have to wait for the sun to come back to perform that test. The Romans didn't call this place 'Hibernia" for nothing, you know...
This allows the Darksleeve to be handled in daylight, but it is prudent to keep it contained within a padded and darkened case when you're not actually in the process of making an exposure. This helps to protect the film from normal handling and dust, and ensures that prolonged exposure to bright light sources will not fog the film. In addition, a single film holder could be contained within it's own light tight envelope, which would also form an additional dust seal, a regimen that many large format photographers follow as a matter of course anyway.