According to "Stress Indices for Elbows with Trunnion Attachments", EPRI TR-107453, Final Report December 1998:
Bend on trunnion
Flexibility factor:
k = 1.01(d/D)^-0.372 (t/T)^-0.12/h for in-plane moment
k= 0.146 (D/T)^1.41 (d/D)^0.36 (d/t)^-0.61 for out-of-plane moment
0.34 ≤d/D ≤ 0.85
It shows the flexibility decreases as trunnion diameter becomes larger in in-plane moment.
However, the out-of-plane moment flexibility factor increases as trunnion diameter increases.
For stress indices (or SIF), it decreases as the trunnion diameter increases except torsion moment.