Every self-respecting pastry chef will always tell you that to make good desserts you must respect the portions religiously. Pastry is pure chemistry and invert / modify / forget an ingredient will result in a disaster. This is especially true for leavened dough and classic cakes.
But often the popular wisdom and experience of our grandmothers will cause us to forget this advice.
I remember my Nordic grandmother and I never once saw her respecting a recipe (except sometimes to smear the recipe book with dirty fingers): all floured and unkempt looking like a mad scientist. But her cakes were always delicious!
My general advice is to keep as close as possible to the recommended portion, but the imagination should always be cultivated: try, experiment, and you will have great satisfaction!
Rome is not famous in Italy, let alone in the world, for its cakes. It has few recipes and poorly sugary. I obviously find them delicious because I associate a memory with each one of them.
This is why all the recipes, except for some inclusion of the Roman and Jewish Roman tradition, are from my maternal family of Northern Italy and from friends not roman.