Don’t just rely on just a straight row of the ten across under the beam as a sideways collapse could occur. Your existing acrows are also in a straight line and some appear to be leaning. The strong boy brackets used induce tortion on the acrow which is not good so they could do with bracing also. I presume you intend to genie the UC beam up to be firm under the plates of the strong boys, acrow up and then shim up the gap in places between the strong boys. This would relieve the tortion effect on the existing acrows. As a bare minimum diagonal bracing could be inserted between the two rows of acrowsmom going to brace beam when in position David, in the top webbing with acrows,, I’m hoping it will be good enough! View attachment 419779