Luckily I'm making new pups so i't no big deal, but a valuable learning experience. I used an imperial drill that gave a snug fit.I think using a slightly larger hole will give the grommet room for expansion. The other mistake I made with the first of those two grommets was belting the installation tool too hard.
Edit: to avoid a double post , a quick update. I wound a test pup using red ironbark flatwork. Wasn't sure if I had enough wire left. Turns out that I did and the ironbark worked out. I also tried using a slightly larger drill to install a couple of rivets/grommets. That also worked , no splitting.