I want to make the QID Merry Go- Round but it is a 12" square (8 sided pinwheel) I want to downsize it to 6" square. How do I do that.

Cut the measurements in half.

I think you might need to make templates. Try with graph paper.
Usually to increase or decrease the size of a block you substract 1/4" on all
sides, reduce or increase the block then add the 1/4" back. But this is a bit
of a tricky block.

I don't know the pattern you are asking about. When googled, I see there is more than one version, and totally different.

The one looks that it'd be easy enough to downsize just by just by counting the squares and reproportioning. The other was a hex-style block, would be easiest done as a tube quilt, and too, easily re-sized.

Start with the finished size of block and likewise for each piece, then be sure to add the seam allowances for each piece.

It's not as simple as dividing the original piece measurements in half.