@ kapuhy
Talking about the armament of your upcoming new unit, I have noticed that those boats came in a variety of different outfits (i.e. Sub Chaser, Torpedo Boat, Gunboat, Rescue Boat, etc). Each type differed from the other for its typical armament, though there often was an additional degree of customization from vessel to vessel.
On this topic you, the following readings might be of some use:
http://www.ww2ships.com/britain/gb-sc-001-b.shtml
http://www.navypedia.org/ships/uk/br...fairmile_b.htm
http://www.navypedia.org/ships/canad...fairmile_b.htm