Here's some centering rings from the Pigasus and Little Green Man kits.
On the left is the lower engine mount centering ring. The ring is punched for movement of the engine hook - pretty standard.
On the right is the upper ring.
On the bottom is a second smaller "relief" for the upper end of the engine hook. This allows an easier fit over the engine hook and the engine tube won't be compressed inward.
Right above that is a small hole for the Kevlar to pass through. Again, no extra pressure on the engine mount tube.