I definitely recommend a proper gourd, the curved side of the gourd allows the mate to kind of shape into it.
You may want to position your bombilla in a way so that it kind of holds everything up and supports montanita. You can use the bombilla to press into the mate to form a wall of mate.
Another component is dust content, which I think rosamonte has fairly low dust. Basically the dust kind of acts like a glue and holds everything together.
Argentine style cut is more prone to this issue. I found La Merced, De Campo had a bit more dust and I had no problem with it. You could also try a Uruguayan style such as Canarias, or Chimarrao which have its own set of challenges to prepare such as clogging the bombilla.
Just remember that there really isn’t a right or wrong way to prepare it. If you enjoy the experience it should be good enough.
I’ve always said it like this:
“Socialism for the things we need. Capitalism for the things we want.”