I have found the 2flute 25mm center cutting insert endmill works great for maximum MMR on the 1100 S3. In 6061 or 2024 I run it at .100DOC, .700WOC, 2500RPM, 50IPM. Calculates to 3.5 cu. in/min. Yes that is .010/flute. The inserts made for aluminum cutting do just fine. The spindle load meter needle is near the top of the green. I cut the feed rate to 25IPM when feeding into the cut since the WOC will be greater, or use an arc for the approach path. I had a job a while back where each part started as 20lb and finished as 2.7lb. I was able to cut the total time per part from 8hr to 5hr compared to roughing with a 5/8 endmill.