Meteor cluster, can I use IP address instead of sub domain for balancers?

From the readme:

Making your instance a Balancer is pretty simple. Just export the following environment variable.

export CLUSTER_BALANCER_URL=https://subdomain1.domainname.com
export CLUSTER_BALANCER_URL=https://subdomain2.domainname.com

Can I use ip instead?

server1: export CLUSTER_BALANCER_URL=https://server1_ip
server2: export CLUSTER_BALANCER_URL=https://server2_ip

Did you ever find the answer to this? I am interested in this as well.

Could you just try it and see if it works?