Some basics -
The only way you get a 9.5" FINISHED block out of a starting 10" square .....is if you do NOTHING to it .
No cutting, nada.
Just sew it to another 10" square. ;-)
Any cuts, even one, will result in a smaller square.
For a 9" FINISHED block, starting with the same square, you can only have ONE
straight cut.
Which eliminates the 9Patch, Rail Fence and the HST.
So on to Plan B.
HST - the EXACT formula is desired FINISHED HST block size PLUS 7/8" for the size of the starting squares.
As woody pointed out - working backwards - you'd get a FINISHED 9-1/8" HST block from a 10" square.
Generally, though, many folks, including myself, start with a larger square, make the HST blocks, and then trim down to the exact size.
You get a perfectly sized block this way.
Since you can't make your starting squares any larger, your only option - and my suggestion - would would be making your FINISHED blocks smaller.
You also might not want to deal with 1/8" or 1/3" increments. I certainly wouldn't.
Both the Rail Fence (if it's a 3 rail block) and the 9 patch block are on a 3(x3) grid.
You're starting with 10" blocks - that's a given.
Taking into consideration the needed 1.5" total need for seam allowances (.5" for each internal seam and .5" for the block seam allowance), the size of the FINISHED triangle, and the least amount of wasted fabric, I would shoot for 8.25" FINISHED squares (8.75" UNFINSHED).
This means you really have just a tiny bit of little wiggle room - the starting squares have to be 10" square and your cutting and sewing and pressing have to be pretty right on.
HST blocks:
Take two 10" squares, right sides together.
Draw a diagonal line from corner to corner on the back of one square.
Sew 1/4" on each side of the line.
Cut apart on the drawn line.
Gently press the seams.
Trim the blocks to 8.75" UNFINISHED
Here's a random link - Method One - explaining it further (if you're not familiar with this method already):
http://quilting.about.com/od/quickpi...uaretria_2.htm
I'm not sure where you're incorporating your other fabrics, nor how much variety you're looking for, but you can see that 3.25" width will work for both the RF and 9P blocks.
Rail Fence Blocks:
From the 10" starting squares, cut three strips 3.25" wide.
Mix and match (and/or use some of the blenders)
Sew three strips together.
The block should be 8.75" wide (the length will still be 10" ).
Trim the block to a 8.75" UNFINISHED square.
9Patch blocks:
Cut 3.25" strips from your starting squares (and/or other fabric)
You should decide on your color/value scheme/layout as it will make it easier to decide which way to press the seams.
Think about this step BEFORE you start the next step.
Life really will be simpler. ;-)
Sew three strips together.
Mix and match the fabrics in the sets for more variety (if that's what you want), maybe incorporating more of the blender coordinates into the mix.
Up until this point, it's the same as for the RF blocks.
Cross cut the above strip sets into three 3.25" wide strips.
Assemble into 9Patch blocks.
These 9Patch blocks
should measure 8.75" UNFINISHED.
-----------------
Ignoring the additional fabrics you're adding, each 10" starting square will render an 8.25" FINISHED square (in some fashion) for your quilt.
So in an 8x10 block layout, the quilt size will be approx 66" x 82.5".
With the additional fabrics, you'll be able to make it even bigger.
Love, love, love Japanese fabrics.
Sounds like your quilt will be lovely.