I'm guessing that that is a 1" spindle. You may find that it is a bit too light for that task. The MF10/12 tractors can put a serious pull on the bottom edge of a back blade if it hooks up with a rock or root. Leverage will do the rest.
When I had a FEL on my 12H, it had enough rear axle torque to jackknife the tractor frame and break the weld on the frame splice when the bucket stopped in a pile of dirt. I can easily visualize that spindle getting bent if you hook something solid at speed. The tractor is a 675 lb sledge hammer. That's over 2900 pound feet of force applied to the cutting edge at a 3 mph impact. The weight of any applied ballast plus the operator increases that force load. The rear axle torque also adds.
Making that pivot too strong is never a problem. Whole different ball game if it's too light!
Edited by TUDOR, January 20, 2016 - 11:28 PM.