Two notes about the plywood ring supplied in the ARF.
1) the wood is crap and delaminates easy. There is very little ahdeasive in the laminations so it splits or the face layer pulls off easily. Ive seen this already happen on the tail gear bulkhead when the mounting block pulled off a layer of wood.
If you drill it on edge go back and add thin CA to protect it.
2) the laser that cuts the wood had a beam divergence which makes the edge beveled not square. Use this to your advantage and orient the part to match the cowl taper. Whether your just mounting the cowl oer plan or doing this mod the angled edge will be of some assistance.

Once the cowl is centered and mounted go back to the back edge that is over hanging the cowl ring. Now sand off the excess lip and make it flush with the surface of the plywood.
I glued the hinges to the plywood cowl ring back face with CA carefully making sure of position and keeping them flush to the cowl.