What has growth been like in sedevacantist chapels during the Church crisis?
1. The only sedevacantist organization that has grown substantially and is all over the U.S. and many countries throughout the world is the CMRI which includes their chapels and the independent chapels affiliated with them.
http://www.cmri.org/The CMRI unlike other organizations has two types of clergy. They have religious that are part of the CMRI and they have secular priests who work with them and run their chapels, but they are free to leave if they choose. They also have at least 3 orders of Nuns, the CMRI sisters, the Congregation of the Mother of God, and another order located in Idhao, I can't remember their name.
2. There is the sedevacantist organizations Trento in Mexico which has many chapels. The Trento group is very friendly with CMRI and they work together at times.
http://www.sociedadtrento.org.mx/3. There are many smaller groups such as the St. Gertrude's group and there was a small Benedictine order in Alabama, but they went to the Conciliar church. I have heard that some would not go along with the return to the Conciliar church and are now trying to rebuild the order with the help of CMRI.
4. In addition to this, there are scattered all around the world, many former priests of the Society of St. Pius X, who operate independent chapels. There are other clergy too, former CMRI and some others that operate independent chapels. A few of the former SSPX clergy that I can think of offhand are Fr. Joseph Collins, Bp. Neville, Fr. Daniel Ahern, Fr. Zapp.
5. The SSPV is also a large group, but they are not strictly speaking sedevacantist.
It seems to me that if one wants to see the organization that has stood in front and has grown substantially with chapels, schools, and vocations it is the CMRI. They are the largest traditional group in the world outside of SSPX.
I hope this helps.