As expected, I managed to get the plug made up and am trying it for size in situ with the bike and sub-frame. I need to clean it up, put nice radiuses on edges and give it all a polish, so its ready to create a nice mould from.
It's all a bit dusty at the moment, where I've sanded or trimmed bits, but I'm actually relatively happy with its fit and how it will look on the bike once I make the final part from carbon fibre.
Here you can see the shaping around the gas can for the shock
It's a good volume airbox considering the tight area I had to work around
Will update this thread with the airbox plug out of the bike all cleaned up and ready for the mould creation