With a Brand New engine-- I think you will be fine. I'd get a Frank Bowman ring right away. Don't even bother with the stock ring. The stock ring has a rounded side to it. It has very little surface contact with the cylinder. This makes the engine break-in fast, but allows for a lot of compression blow-by. Franks' ring is more straight sided, and has very little ring gap. It's a nice fit and will help performance a lot. Frank can send you a ring for around 12--$15. It's easy to replace the ring.

Go to some of the local small engine repair shops and try to get a bigger crab. I know the Walbro WT348 is a drop in replacement for the stock carb-- only bigger. There are probably several carbs that will bolt up. Just make sure they have the pulse hole in the same spot- so it lines up on the intake port when you bolt it to the backplate.

Small engine repair shops and lawnmower shops are a great source for parts. I'd count on spending $15 for a carb rebuild kit if you decide to buy a used carb for it.

As for the trade of my 38cc engine------I would trade it for almost new JR coreless or Digital servos(8101--4131--4721--8231--8411). Not interested in Hitecs or anything else- just JR servos.