HP ratings should list a RPM at which the listed (or peak) HP was obtained. Often this RPM is above the ideal RPM range for the engine. In addition, it isn't always clear as to how the engine was setup, i.e. which fuel, what nitro, did it have a muffler or was it open exhaust, etc. You also have no idea on power curve with a peak HP rating. For these reasons (and probably others), the HP rating listed for a engine doesn't mean a whole lot.

If you want the most bang for your buck, 2-strokes offer cheap power. However, there are some advantages to 4-stroke engines, mainly they develop their peak HP at a lower RPM which means they can turn a larger prop compared to a similar sized 2-stroke.

Typically, the weight of the engine doesn't matter a whole lot unless we are talking about an abnormally heavy/light engine. Obviously CG can be effected, but overall plane weight (i.e. wing loading) won't vary much between diff engines in the same displacement range. However, the power diff between engines of similar displacement can be large, which is significant.

I'm not familiar with your plane, but the engine you are using is at the low side of their suggested range. A bigger engine will help the underpowered problem. As for the brick problem, does the model weigh what it should? Is is balanced properly? A nose heavy plane can feel !QUOT!brick like!QUOT! in the air.

If it was me, I'd probably use a YS110 (that's a four stroke) for your plane.