RE: Flaps or flaperons?
Here is an easy test to determine if it is a power system (prop, engine, RPM) issue, or control (setup or procedure) issue. Get up to altitude, ease back to idle and try to hold altitude. If the model does not descend or still can climb it is a power issue. If the model just goes into a slow descent at full up elevator it is probably not enough elevator control (could be not enough throw, nose heavy, or a combination of the two.) If the model will slow until it stalls, then you are just not slowing it down enough on approach. Now if the model goes into a stall, but at a higher airspeed then a Cub should, then it is most likely very nose heavy, overweight, or a little of both.