I've just made an executive decision! My 24 1/2" block I have ready I will still do rounds for but it will end up as a cover for my washing machine. The 12 1/2 " block I have ready will continue, adding rounds as directed and I like the idea of making a specific centre for one as well. I'm ready and raring to go....3 to do. now to look up the Mariner block...looks hard,may take a bit of thinking about, but I love the look of it.