I don't think I've had enough coffee yet. My first stab at this is if count the number of rows going up -- from the picture I got 32 (which may not be correct). You already have the seam allowances built in so don't need to worry about that!
If 32 rows = 74", then adding 1/2" to each row (regardless of size) should be 16" (32/.5 = 16) for a square of 90 (74+16).
Likewise, if you went 3/4", I get 24", or 74+25 = 98" which for me would be King sized.
You would also need to add some to the width of the strips but brain has not fully digested that part
I am only 2 cups of coffee in for the day, but I think that will work.
Edit: Second look, maybe you don't need to add anything to the length of strips by the way it is constructed. I'd have to draw it out to verify but I think the .5 or .75 is a good head start!