I thought I'd be smart and cut a big hex in half. Doesn't work! You have to add the 1/4" seam allowance to one half which makes the other half too small. Then if you don't cut it in half on the straight of grain you have a big problem. You have to mark the grain on each hex before cutting or have a terrific memory. LOL. Missouri Star has the 10" hex ruler on special right now if that helps.
http://www.missouriquiltco.com/catal...3+Half+Hexagon