Glad to hear about your progress!
I would say you should keep doing what works best for you, until a different technique proves itself better to you.
There are a few points I would have to observe to make a recommended change in your technique. For example, you may have a putter that has the putterhead offset from the hosel a little. And it's not real clear to me where the exact bottom of your stroke is located in relation to where you like to play the ball. And also, the precision of the way you return the putter face to square at the bottom of the stroke matters, as does the sort of grass and grass condition you play on.
So it's a little hard for me to comment about how you are playing the ball. I will say that many people like a descending blow of the putter through the ball.
On the one hand, you may not be making a great ascending blow, so comparing one ball position (forward) to another (further back) is not really an equal comparison. On the other, there may be reasons why the ball position you like is giving better results at this time due to your putter, stroke or your greens.
My general approach over the years has been to be patient about changes and also about keeping an existing technique. My experience has been that the better approach will eventually force itself upon you, so long as you keep open to improvement and keep paying close and honest attention to how your technique is actually working. Apparently, at your stage and in your particular circumstances, your present ball position is the one to stick with for now.
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