Brass work for Gladius in process.

[Crispvs]

Most surviving cross hangers only have nail/rivet holes at the back, suggesting that a lot of them were nailed to their scabbards from the back, which would be in line with how they assembled many other items, such as pugio handles. Some cross hangers do feature holes in both front and back though, indicating that rivets or nails passed right through these scabbards. Unfortunately museums don't tend to display scabbard parts in a way that lets the backs be seen and neither do books. However, it would not surprise me to find that nails had been used with the points clenched over at the back. Dagger sheaths were sometimes assembled this way, although some were riveted instead. I am not certain though what practice was used for attaching cross hangers to sword scabbards where the rivet/nail passed right through.
There are others here on RAT though who will know more. If you haven't already contacted Matt Lukes, do send him a message, and Christian Koepfler (Gaius Beerquitius here on RAT) may also be able to help.

Regarding hose fittings, that was pretty much what I used, as you can see if you have another look at my sword and scabbard thread. They were quite a lot of work but I was very satisfied with the result.

Crispvs