So that’s the other thing. Power/torque has never been our issue, it rigidity. the first three aluminum milling videos I put up were with 42oz/in steppers. The only reason I upgraded the kits was my supplier offered them at the same price. There are a ton of factors. The biggest one you will need to worry about since you seem to be going for aluminum milling machine is the shortest legs and z axis as possible to maintain rigidity.