I don't have the book, but I do know that 6 inch blocks are a fairly easy size to upsize. Doubling up the size to 12 inch finished blocks shouldn't be that hard. The key thing is to look at the finished size of each piece, say it's 2 x 2. Normally, you would cut 2 1/2" squares. To double that up, you would do 2x2 = 4 for each side of the block + 1/2 inch seam, so you would cut 4 1/2" blocks. You have to allow for the seam allowance separately. I use EQ7 when I want to do that. Graph paper works just a well.
To do a 9 inch block, you would do 1 1/2 of the original finished size. So, a 2 x 1 piece, would end up 2 x 1.5 = 3; 1 x 1.5 = 1.5 so you would cut 3 +1/2 inch for seams 3 1/2 inch by a 1.5 +.5 = 2 inch.
And, no, I wouldn't make a block with that many pieces as a 6 inch block. Quilting should be some fun, and that would only be tedium for me.