well, go ahead and grind it down yourself, sounds like a very precise art. I see your reasoning behind not drilling holes, but obviously factories have already done it. If you do it right, you won't have problems with cracks. The cylinder wall below the rings would not be considered a high stress area. Plus, circular ports have no stress concentrations, so the threat of cracking would be minimal. I find it funny that you put down precise cnc milling, suggest grinding it with a dremal tool or something, yet say that drilling precise holes will develop cracks. Your thoughts seem mixed. Also, to say it adds strength and increases durability seems very oldone-ish. Provide some proof, I'm curious. Not saying your wrong, but you leave me with mixed thoughts to your reply.