Hey Rhonda, I also have the 9” block set and was not able to use it for the mystery because the dies cut pieces that are too big. I think the folks who used dies from one of the block sets were using ones from the 6 inch block set.
Even though the blocks for the BH mystery are 9 and 1/2” unfinished there are A lot of pieces in each block which is why the dies from the 9 inch set ended up being too big.
Someone did post the die numbers for the dies they used on the thread here on the board- if you go to that thread you should be able to find the info.
OTOH- if you are looking to enlarge the blocks, then I think there are a couple of dies in the 9” set that could be used.
Also, my understanding is that there is one piece in the quilt that has to be cut by hand because there is not a die available that will cut that shape in the correct size.
Rob