You might want to model this in BeamCalc or some other tool. The spreader plate will tend to distribute the load across the entire 330 mm span, modulo a decrease in shear as you go across. If this is in a seismic zone I would visualize the entire structure placed on a shaking table and secure it...
I usually cross check structural calculations like this with BeamCALC or some other tool.
The bookkeeping along with units variations can cause errors to creep in.