I am right handed. I shoot 3D. Distances till 60 yards. A year ago I lost my eyesight on my left eye, due to MS. It recovered a bit but I am still not looking good with it.
All you need is practice, program your brains. Make the distance bigger step by step. On short distances I shoot purely instinctive, looking at the target only, at bigger distances, I shoot split-vision. This happened automaticaly with me. I think my focus is for 75% on the target then and 25% on the arrowpoint. I "put" the arrowpoint on the target.
Another thing to remember is your FOC. Where you use for hunting a large FOC, like 20% or more, we use for 3D in the range from 7-9%.
Most 11/32 wooden arrows with a 100 grains fieldtip will give you this. You can also use Stu Miller's dynamic spine calculator.
Any questions left? Shoot!