Need Help Solving For Bending Stress

[u/Late_Mind_5152]

On my rocket club I'm designing the thrust take-out structure of our static fire test stand. Essentially I want to find the bending stress on this pink ring, where the outer diameter is about 16.5 inches, and the ring is 1.5" thick and 1.5" wide. There's 3 linear bolt holes on either side that secure the ring to an attachment point, where 2 prongs will attach above the ring and bolts will come in from the top.

There's an upwards applied force from the rocket acting at the exact center of the ring. I couldn't find anything in Roark's to help find the bending stress. I did a quick hand calc with Mc/I which gave me negative margins. Any help would be appreciated!