Drifting

I am working on ideas for a series of iron window grilles to be mounted on the interior of five windows. The client seemed interested in having glass incorporated in the design and when I saw pictures of some work done by a friend starting out with art adventures I thought the marbles he was using might provide a solution.
I have been practicing slitting and drifting bar to house the marbles. The bar below is 25mmx9mm and I drew it down in some sections to about 17mm and 21 so that the different sized holes I wanted to drift would have similar sized walls.
I watched some videos on you tube and made some slitting punches and drifts.
This bar is my second go.

Here are the two slitting punches and one of the drifts with the bar after having the slits drifted out to three different sizes.

With the marbles laid in the holes on the bench it didn't look very impressive, so I used a few blobs of hot glue to hold them in place so that I could hold the thing up to the light as seen below. I expect I will be able to weld this test section into the finished piece somehow once I have done a bit more testing and finalised the design a bit more.