I recently kit-built one and powered it with a .46LA. It took about an ounce of weight in the nose to balance with the RX and battery as far forward as possible.

The landing gear area seems plenty strong as designed, if the ARF is anything like the kit. My dry weight is right around 4 pounds.

I have only flown it about 4-5 times so far, but it is a lot of fun. The ST-45 will make it haul. You should be able to balance it by moving the battery back.

The biggest downside to the ST-45 will be flight times. They are pretty hungry engines, and the plane only has room for a 6 ounce tank.

Good luck