For a few years I used a Big Stick 40 for an engine test and break-in plane for both 2 strokes and 4 strokes. I counted one time and I ran 16 different engines on it. You can see on the nose shot that I have an external throttle pushrod. I used this for 4-strokes.

The smallest engine I had on it was a Saito .56 and it wasn't nearly enough power. The largest engine was a Magnum .70 4-stroke. Power was OK, but not as much as a good .46 2-stroke. I aso have 2 Magnum .52 4-strokes and, while they are good running engines, they would be better on a lighter and slightly smaller plane.

It does build nose heavy, so I moved the rudder servo to the rear and added 2-56 rod tail braces, as shown in the photo.

A .46 is excellent. The Maggie .52 XLS or an OS .55AX will really haul it.

I would suggest building the plane without the rudder & elevator servos. Then tape or rubber band them on the outside to check the CG. You may need both mounted in the rear.