When I draw 3"/50 for 165ft "A" class I've used original photo, resized to the Shipbucket scale. So the proportions of the gun seem to be maximally close to the original.
But yes, according to SB standards, this gun drawn this way looks smaller than other comparable guns. But I'm not quite sure how to redraw the gun to look more Shibucketish, but preserve the real proportions and dimensions. I suppose I must abandon a little fidelity to match SB requirements and standards?
So the result is this: