I did a little pattern drafting and some calculations and came to the conclusion that if you increase the finished size of each of sides of the cut pieces by 1.75 you'll get a quilt that is approximately 91" X 105". I used 1.75 because this resulted in cutting sizes that have fractions that are evenly divisible by 1/8. Otherwise you need to deal with fractions such as 3/5 and 1/3.

The attached pdf and gif show the cutting sizes as used in the pattern and gives the new cutting sizes for a 91X105 quilt. You'd probably need to test the snowballed ribbon end blocks because my version of EQ7 does not do snowballing. I hope you can link to this because I wasn't able to keep the formatting when I copied the table directly into the reply.

thanksfor answer

Thank you all for your ideas!
I guess I had better get some graph paper and colored pencils out. The friend I'm making it for says to keep the ribbons the same size as the throw, but I may want to increase the width of the ribbons anyway.
Maybe I could have some ribbons starting in the middle area that will be on top of the bed? What do you think?

How do you figure that doubling the size of the pieces equals multiplication rather than addition? It would be the same as making twice the number of blocks.

If you double both measures (length x width) that is multiplication.
a 6" x 6" block is 36 sq inches, doubled both sides is 12x12 or 144 sq inches
This is the same as making 4 times the number of blocks.

If you only double one measure (length OR width) that is the same as doubling the number of blocks.
6x 6 (36 sq") becomes 6x12 - only 72 sq "

Thank you, Quilting Chris, for your drafting work and calculations. You're a whiz at this! I will use your chart and its measurements!