I think your center points match very well, indeed!
One idea, you may have already done, is to start in the center of the block and sew outward, rather than starting at an outer edge.
When you stitch the 2-two block sections together, it will be even more important. Because you are starting in the center, working outward, you may want to start with very tiny stitches for the first half. When you return to center, place your needle down so that you will be stitching directly on top of the tiny stitches, this will lock your ends in place. Three or four of these locking stitches, not so tiny as your first set will do the job admirably. :thumbup:
And, always remember! If those are your practice blocks and look that good? Those are probably the worst you will ever do!
Good show! <wave>