Why not?
The leather gasket is what worries me. Depending on how that gasket is finished, it could be extremely hard to make the silicone disappear if it bulges out a bit. The pores in a lot of tanned leather (like a baseball glove or bomber jacket for instance) are open, and any silicone that got on it would never come off, and would leave a stain that says, “hey! I’ve got silicone gobbed on me”.
In order to ensure that wouldn’t happen, the silicone bead would need to be tiny. If it was that small, I’m not sure how much good it would do, anyhow.
If the leather was finished to a shiny surface, then yeah, I would do it.