This seems too wide to me. I have ordered a 7 1/2 inch gullet and am shimming my 8 inch until it arrives but am worried the back may still be too wide?

Keep in mind, you are looking at leather - the tree is way up from the skirts of the leather (I figure that is what you are meaning is too wide).  If it's even pressure under the tree, you should be ok.

Okay, good point! Thank you!!