>>> How do I approach the repairs on the really large areas and holes? I think I have to shave some fibre and combine these with the 3D bond and then apply.... I think glueing rather than stitching is going to be required as the hide although more flexible is still pretty fragile in many areas.

1- Getting the alignment without distortion before bonding it is the priority.
2- The bigger pieces are put in place and then following in according to reduces piece sizes.