What is sufficient in hitting the target?
We use what are called "null" targets. That is a standard IPSC target with a 3.5 hole sawn from the middle. The object is to shoot through the hole and not shoot the cardboard. Thunder Ranch uses the same target and that is where I stole/borrowed/lifted etc. the idea. The thought is you should hit the hole at speed, and then extend the range until you are hitting the cardboard then work on your accuracy until you can hit the hole at speed and then extend the range again.
We like the null target because if you shoot correctly, you are looking through the sights and not looking for the hole in the target. It re-focuses your eyes on the sights not the results of a hole in the paper. If you are shooting well, there is no evidence on the target... you learn to trust the front sight by watching the sight...not by diverting your attention to the paper... works very very well... At the dept. I work for we start all new shooters on Null targets to refocus off of their performance on paper and onto trusting the sights....
So if you can hit a 3.5 inch hole all of the time at speed...I think that is good enough!
.... peg the happy guage!