Eccentricity of load causing shear stress from bolt group centroid.
Polar moment of inertia
$$ I_{bg} = {\left({ n_{c_{bg}} \cdot {n_{r_{bg}} \over 12} }\right) \cdot \left({ s_{r_{bg}} ^ 2 \cdot \left({ n_{r_{bg}} ^ 2 - 1 }\right) + s_{c_{bg}} ^ 2 \cdot \left({ n_{c_{bg}} ^ 2 - 1 }\right) }\right)} $$
Critical bolt horizontal force
$$ F_{3_{bg}} = {P_{bg} \cdot e_{s_{bg}} \cdot \left({ n_{r_{bg}} - 1 }\right) \cdot {s_{r_{bg}} \over \left({ 2 \cdot I_{bg} }\right)}} $$