During a long printing session I first checked the focus over the entire printing area.

I then printed the first (5x7") negative using a glass carrier, put a second (13x18cm) negative in a glassless carrier, printed that, next a 4x5" negative in another glassless carrier, and finished with a 9x12cm negative in a second glass carrier.

Never once did I adjust focus or realign the enlarger, I merely swapped paper sizes. All prints were sharp from corner to corner.

BTW, I used the same 180mm Rodagon lens too. And the enlarger is a Durst L138S.