Kempster B was a pulsed gun. Haven't found anything more than that but it was likely much lighter and smaller than A. One report mentions a weight under 90lbs per gun being possible with further development, and ~78lbs an optimistic but achievable weight with more funding.
For x-ray shielding there is a report that makes estimates for required lead thickness in the q-bay. This is highly dependent upon what film was being used. 4404 needing none, SO-206 would have some fogging without shielding, 4400 needed 0.6mm of lead on the aft bulkhead and 4401 required double that.
Oh and there are quite a few flight reports that confirm flight testing. Very likely that Kempster A and B were flight tested based on the dates of these tests.