Need some FT Help with weapon design

Hello all...

1 of my buddy has a want for a Ship with B3/B4 Firepower but only 12
Range, 
and I have been kicking around the wgt for 1 of these.

What have have is a B3 at Mass of 2 and only allowed 1 arc and a B4 at
Mass 
of 4 and only allowed 1 arc.

Have I made these to 2 Powerful?
Any thoughts or Ideas on how to better work it?

DOC Agren

     (Lurker on the Digest)