You should plan for the provision of keel before you start construction.

Becuase this is not a racing boat the placement of the keel is not critical.
Although considerations of the lateral profile will affect performance. Don't wory about big thoery, for scale sail it is not rocket science and it is simply laid out in the books recommeded below.

Traplet publishers do a couple of useful books
https://sslrelay.com/s84068217.onean...dex.shopscript
Historical Sailing Models by Martin Becker and Radio Controlled Scale Sailing Models by Phillip Vaughan Willaims both have informaion on keels.

The following images were taken from these pubs.

As you may be aware you probpably need to reduce the sail plan and increase the size of the rudder, if you are turning a scale model into a working model.

There are other things you may need to know as well. I would strongly recomend the Vaughan Williams book.