Okay, after looking at the pattern, there's going to be A LOT of calculating to get the larger strip size to work. I mean A LOT. I would add borders to enlarge the quilt. Do the center per the pattern, then add one or more borders of your favorite fabrics that you used in the quilt

I totally agree!!!!!!!

You could try making a couple of the blocks or a wall hanging to "see how it works" - and then you might have a better idea of how to change the piece sizes.

If you are a comparative newbie and math is not your thing, I would strongly suggest doing what PaperPrincess suggested.

Or you could graph it out on graph paper and enlarge it that way.