We're making double wheels today. The truck I've showed here on Monday has a skinny carriage, that means it had to be balanced out by chunky wheels and large axes, so that it doesn't cant over with the load, or without. The airplane has been pretty stable, and still is, with the single wheels, but that car model clearly "asked" for double wheels. And double wheeled we went.
A quick note though: to get them assembled safely and minimize the break risk I pulled the wheels off from axes right after baking, put some strong glue into each wheel and got them back together. Now they can surely tolerate more off-road tours.
And about the whole process all-in-all: I'm far away from thinking it's the best way of making wheels for a vehicle, and of course I need time to see how child-proof it is and how much use it can endure before getting broken, but for now it's enough. I have to experiment with another materials, re-using, re-purposing and trying to find a way how to improve that system. That car is running slightly "duck-y", which means I haven't adjusted the wheels well enough. That's not necessarily bugging me, but still something I'd like to get better next time. I'll keep you posted!