Usually there will be a tapered section mear the bolt where the sides are cut away. That needs to be kept to the inside of the curve.
Your stem doesn't appear to have that cut, so odds are it depends on the stem being spread open (slightly) and oriented so the long dimension of the oval is radial to each curve.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.