A friend had a Magnum 30 and it would not pull a 10 X 6 when new without getting hot. His first flights were with a 9 X 6. Soon he moved the engine to another plane and went to a 10 X 6 prop and it ran fine. He also has a Saito 30 and the Saitos pull 10 X 6's when new.

I have three Saito 30's and and a OS 26 for about 4 years. The OS 26 seemed to like the APC 10-5. I also had a Magnum 30 which spun a 10 X 6 as well as a Saito. I never ran anything but a 10-6 on my Magnum 30. It ran exceptionally well with the 10-6. The 10-5 props didn't do much for my Saito 30's. I just ran 10-6 props on them. I only tried a 10-5 on one off them on the bench.

Bottom line is some Magnum 30 engines are better off with a 10 X 6. Mine ran close to 11,000 with a 10-6.