Shooting off your knuckle will require that you match your arrows as close as possible to the right spine weight.
There's a plethora of information out there to be read on archery in all of it's forms. If you haven't had the chance to read some of it, you are in for a treat.
Be forewarned... it can lead one to thinking that they too can make something as simple as a bow that will fling an arrow...lol
I doubt there is a greater thrill than taking your intended game with a bow made with your own two hands, with an arrow of your own making (yuck)...lol fletched with wild turkey feathers from a bird you killed, launched off of a Flemish twist string also made with your hand.
I'm sorry for the short detour but just thinking about archery leads me not only to wanting to be in the woods today but brings back such sweet memories. Some(like the one above are mine) but others have also written about it with much detail and love. It literally begs to be read, enjoyed and shared by joining in making all aspects of it a part of your journey as well. If it's your desire to feel the archer in your soul.
God bless,Mudd