In the 12 years of the Great North East SxS Classic, scores over 90% have been uncommon.

I believe the 2014 main event was won with 85%.
Each of the 6 side events by gauge were won with 86% or less.
I know this because the shooters actually carry scorecards.
There is no requirement that they be used or turned in, though.

I doubt the Bo-Whoop event has ever been won with a "light game" gun, though the purse money can be won with a SxS of any vintage and/or manufacturer.