As has been mentioned above Bill, you can do it, but you will need to eliminate or modify the brass tube. I am assuming you want to start with a kit, because you don't currently have the ability to do your own threads.
If the material you are using does not need the support of the tube, ie. acryilics, then all you need to do is drill two holes. One, just wide enough to fit the convertor, to a depth that will accomidate the convertors lenth. I would have to check my books, but 8mm comes to mind. The next step is to drill a larger hole to fit the adapter piece that the section screws into. Drill just deep enoug to take the adapter. The adapter will get epoxied into the hole. This will allow suffisient material, at the finial end, to make a taper for posting.
The biggest problem with this method is how to hold the barrel for final shaping. If you have sufficient excess parts, you could take a spare section and glue it to a tenon on a piece of acrylic mounted in your chuck. This would essentially make a mandrel for the barrel.
Another method would be to make the second, larger hole, deep enough to take about 1-1/4" of the kit tube. Once glued in, this piece of tube should be enough to allow you to use a pin chuck to hold it for final shaping. Afterwards, the section adapter could be press fit or glued into the barrel.
NOTE: I have used barrel trimming mandrels to make pin chucks.
Once you start playing with these ideas, the possibilities become endless.
Good luck with the project.