Cheers PD, that's good to know, don't suppose you have any pics of what you did? Or a link to a write up?
Whilst I hatch a plan for the exhaust port I thought I'd crack on with Reb's head mods for unshrouding the spark plug.
Firstly, I tried marking out the way Reb did but, because I'd already polished it, I couldn't see what I was doing so I sharpied the whole thing.
Next I removed sharp edge all the way round turning it into a flat land using a dremel, generating a flat at this point makes measuring what's being removed easy. I worked behind the plug aswell to blend into the larger bore.
Starting to blend that flat into a radius, using the dremel, turning that single flat surface into three, again makes seeing what's being removed easy.