Maybe this will help. Maybe not.
In my opinion on originals you will see trends not rules. Each rifle was an individual and as such was it's decoration. It was up to the maker to decide how much or how little. My limited study of originals confirms this, at least for me.
Keep in mind this is looking at many rifles by different makers from 1770 to about 1800. So this is very general or if you will.....the general trends. As a whole you will see all kinds of stuff. Enough for me to say...there are no absolutes in beavertail and tang finals or lack there of.
This may different if you are studying a particular school and specific maker.
In my opinion a rifle with forestock moulding, buttstock moulding(these can be be simple incised lines), beavertail lock panel finials and a sculpted cheek piece but without Rococo carving really captures the "trend of a Colonial rifle"...much more so than a plain straight up build devoid of any decoration.
With that said it goes back to the rifle and the maker. It's always about the rifle...the rifle. The rifle must be done right as far as architecture. Never sacrifice that for decoration.
What I'm getting at is don't force anything. Do what you feel comfortable with. If you want to do beaver tails without tang decoration by all means do it. Do what you can do and do it well.
Lastly, don't be afraid to do new things. You can do very simple things. Look at Mike Brook's work. Look how simple some of his decoration is, especially the tang. Sometimes it's just a simple shape with some incised lines and chip carved with a small gouge. It's simple but it captures the trend of that style he is emulating. Now he can do much much more but a lot of the times less is more.
