Progressives are no worse then single stages. It all boils down to one simple rule.
After charging the case with powder, look in the case and put a bullet on top of the case right after you look in the case. Problem solved. It's now impossible to double charge the case with a bullet on top. Works on the 550 as well. Put the bullet on the case after looking in the case and before you index the press. Simple and safe.
Ignore Text Size....posting from a phone.