I have a MotionPro chain tool, not sure if it's the one you have. Mine is not for Quad Stake Riveting. I thought that tool was for solid nosed riveting, not hollow rivets. I measured the chain width as suggested using vernier calipers. Outer surface of link plates. I did find an issue with the chain tool. When flaring the rivets, the instructions showed the large alignment bolt pressed up against the link plate with the flaring tip inside pressing on the rivet end. The problem was that the alignment bolt started to turn as I turned the push bolt to flare the rivet. This, started to press in the side link past my previous setting. I stopped when I realized what was happening. I remeasured the chain width and sure enough it was thinner on that end of the link. So the plate width was slightly tapered on the master link. The link was not binding so I decided to leave alone vs buying another master and redoing. Not sure what the ultimate wear or performance will be because of this.
I used a D.I.D chain and the flaring width for a 530 chain was 0.224-0.236". I made the flare ~ 0.228".