I cannot speak for DIR but I do not see any place that forbids a swivel/angle adapter in the Hogarthian playbook. And this is the Hog sub forum, not the DIR sub forum. I (probably) would not want an angle adapter on my 7 foot hose rig and I might avoid them if I were still doing penetration diving. But I do have and use the swivel adapters and like them. I prefer the 110 degree swivels on my open water kits be they on a 40 inch or a 60 inch hose. I find there is less tug on my mouth and teeth and that the hose does not loop outward nearly as much. Keeping the long hose tucked in cleanly, IMO, is worth the extra connection and in use they have not proven to be anything but reliable. As to interfering with air sharing, I have not found that to be an issue, if anything the swivels improve access to the donated primary. YRMV.
James
James