You should call Vans for guidance.
I found this type damage on one mount while performing an annual, not quite as deep as yours & had a welder fish patch a 4130 piece over the damaged area with TIG. Exceptional welder, he was able to do it on the plane. After re-painting the area, I attached a bit of baffle material to prevent future damage from the exhaust. Each annual the baffle material is removed to confirm no further damage is occuring.
Maintain lots, upgraded - repaired - & modified more, rebuild a few, & built some too.
Last edited by Ralph Inkster : 03-19-2018 at 03:07 PM.