Are you at all worried about the bottle overflowing? In my mind (and what I understood from learned people) musk maceration need to be "started", that is, you heat up the oil in either a bain-marie or in the sun, or what I did, as it was winter time, left it near the heating vents for a couple of hours, and then add the musk grain in. I did it after and then you can start waiting for the scent to change.
I started mine in half tola bottles with musk and oil taking no more than about 60% of the volume and that helped because it did expand a little bit. And I'm not sure if this was something I actually noticed or imagined but I remember the bottles "burping" when I opened them, much like when you're making sauerkraut. You also mentioned they were semi-dry so I imagine they'll get larger, probably won't displace the oil but I wanted to err on the side of caution.
Once the musk grains are started, and a good period of time has passed, that's when I fill the bottle with more oil, or empty the whole thing into an even larger bottle. I don't do the starter method this time around though, perhaps maybe I should. 🤔