that is a surprise, but good for the swap I guess.
Just had a thought though..........
It's too late to even contemplate the pluses and minuses, but have you considered carbs on the 4V motor.
Can't think of a particularly good reason other than getting around the under tank issues and possibly some electrical work????
You may have it covered, but isn't the battery going to be somewhere close to the 4V rocker cover and exhaust to?