Being it's a known problem, they should be providing a steel replacement. Cast iron is brittle, but apparently cheap, and has no business being in a stress area.That's pretty ironic for a press with a 2" ram.
Would nice if they'd give you a toggle without the cut out.
Or get the one they give you and take it to a machine shop and see if they could make you one without the cutout.
Or put the new toggle in sell it and get a Lee classic cast. I've used both and prefer the Lee but nothing wrong with the summit.