Rock, The big IF, is do you want your gratings to look like real gratings?  If you do, you will have to make your own or can get them from Syren but I don't know if the scales offered match your kit.  Most kits either laser cut the openings or use  interlocking strips rather than using ledges and battens and most of these are totally out of scale.  I suspect the construction would have been similar even in the 16th century.  If that is the case the below may be of some help to you.  Ke