Looking for help with measurements?

Afternoon all... I am working to create a 3d model of the below steering wheel cover... I am trying to 3d print a version that will mount to the Momo steering wheel that I have... my challenge is I need the measurements of the center horn mount hole without the chrome ring. I think that is a separate part from the silver cover... If anyone has one mounted and can share some dimensions would shave me and my son a bit of time in playing with the measurements in the drafting software. Thanks in advance if anyone can help!

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