I was concerned about the same thing. So, I combined the two short crankshaft gears into one single longer (steel) gear and then secured it to the crankshaft with a pair of pins carefully drilled through pairs of opposing teeth. If you are going to try to use an electric start, the stock thin brass hub might be a problem, but then turning down the crankshaft isn't too appealing either especially if you've already turned it. It's a pretty long run to the cover bearing and a skinnier crankshaft is more likely to take on run out along the way.
You should start a build thread. I'm impressed with your cast cases and would like to follow your progress. It will also be easier for others to answer questions if you have pictures of what you're asking about. - Terry