10" is the only way to go IMO.
Yes, its still possible to bonk a fish off at the bottom of the ice. But I like to increase my odds of turning a big fish under thick ice with a bigger hole. A lot of my ice fishing (trophy fishing) gets done later in the year, big pike on Sak, big walleyes on Winnipeg, big lakers on Clearwater. Hookups on big fish aren't super common, so when it happens I want everything in my favor to get that fish topside.
Up at Clearwater where there is a very good chance at a 20+lb laker, I'm drilling 2 10" holes side by side. My BIL had a 20+lber get off last year because we couldn't turn it up the hole, he had 2 holes side x side but holes weren't straight so he had a little ice bridge at the bottom of the hole. Heartbreaking after a 45 minute fight and seeing the fish 40" away, but couldn't do anything about it.