Fortunately my gym has a new back extension machine suitable for shorter people.
I tried out barbell back extensions using straps, Pete Rubbish style .
Managed 60kg fairly comfortably for a few sets of 10.
Pete does at least 3 plates aside but he did deadlift 900lb. My mid back and glutes were quite sore for a few days. I tried 70kg the second time. They felt a bit heavy but I’m less sore.
Anyone have any experience with these or have reasons why different variations such as dumbbells are better? I would most grateful for feedback.