I'm using an Omega D5XL with Dichroic head and Omegatrol. Best enlarger I've ever owned. And it does allow rotation of the carrier, no problem.
This was shooting with their 80mm N lens, and 210 C. So I switched to the standard 5x7 Speed EZL, and I had even borders and full frame image.
A proper neg carrier is ESSENTIAL when printing any format properly.