Not necessarily , it is up to you. Sounds like you are very comfortable with your present
configuration and is working for you. Take for example legendary conga master Candido
Camero who uses (3) LP fiberglass congas (11 3/4")
https://www.youtube.com/watch?v=U2jIis6Kmq4Pretty much, the standard configuration for what we call Salsa is a 11 3/4" and a 12 1/2".
IMHO your present configuration is just fine. I have this older LP fiberglass conga (11 3/4")
that I like to use as my lower drum and I use an LP fiberglass quinto (11") as my main drum
and it sounds fantastic to my ear. The beauty of them 11 3/4" is that they cover a wide
tuning range, a very versatile drum size to say the least. I hope this helps.