Make hitcircleoverlay.png and hitcircle.png a transparent image.
Make sure the hitcircle design file name is set to default-n (n refers from the numbers from 0-9). Note: The default numbers will be 80% of its original size. So multiply it by 1.25 (default hitbox size is 118px. So if you multiply it by 1.25, it would be 147.5 px, rounding it off, it will be 148 px. you can increase the canvas size to 160x160px though.
Set the HitcircleOverlap to the same image width.
HitcircleOverlap: imagewidth (for example, 160)
Method B:
Make hitcircleoverlay.png and hitcircle.png a transparent image.
Make the hitcircle design filename hitcircleoverlay-0.
If you don't want your skin to have numbers, make all the default-n transparent.