You mean 17-19, not 17-20

1-19 are "no attack" servers, so they should merge into "no attack" super servers.
Bundling an attack server into the merge means you have to decide which direction the super server will go. No matter what decision is made, there will be unhappy souls. This is easily remedied by simply keeping "no attack" and "attack" servers segregated when deciding whom to merge with whom.