Selfbows are not center shot. Arrows have to be spined properly so they can get around the bow(archers paradox). As the arrow bends around the bow the string, pushing it forward, is pulled by the arrow to the left(in a right handed bow)before they(the arrow and string) seperate.
When I shoot I'm hunched forward, my head is down right over the arrow, my bow arm elbow is bent and the bow is canted(I draw 26"). I only use an arm guard to keep my shirt sleeve out of the way of the string, not my arm or wrist.
Keep experimenting with grips and styles and you will find something that works for you. It's not the bow in most cases but the nut behind it! d;^)