The only issue I can see with these is playing behind the slide.
That's the primary benefit of using a slide on your pinky. Sonny Landreth (a few before and many others since) will play additional notes or even chords concurrently with/behind the notes their hitting with the slide. I've dabbled, but my abilities are weak. For us mere mortal sliders, this seems like a good option.
To the thinner barrel, I would think it would require even more precision than a bottleneck style (regardless of material).