Here's a little light reading for you

Read all of the pages as each part has an affect on the next part.

I know it doesn't specifically relate to RC enignes but trust me - the information is good for RC ones too .

[link]http://www.chuckbunnell.com/kart/jennings/jennings.html[/link]

Then when you think you have all of the answers - let us know how you ended up. I personally find experimenting to be the best part of this whole hobby. Even better if the experiments work too

Beware that by grinding ports out, you will reduce the life of the plating in the cylinder. Good plating intrudes very slightly into the port area so that the rings don't catch the raw edge of the plating. A good sanding with some fine wet and dry paper (1200 grit or finer is good) around the ground area reduces the issue.