In my experience making stiff, not tapered and square T.E. Flaps seems to works much better, specially in high wing loading models. My models are quite heavy, which is good in strong winds, but still can turn tight corners. I am firm believer that my planes fly as well as they do because how I built the flaps. In a low wing loading it may not make a significant difference as you will never get close to the critical angle of attack. But if any of you is suffering with stall, try replacing your flaps and sealing them of course.
If this model can handle the weight of an ST 46, then it opens the range of engine choices quite a bit. For example there is the Enya 40XZ which I believe is the lightest and strongest in the 40 range with 9.8Oz with the stock muffler and 8.3Oz w/o muffler.
Here is a video of my Enya SS30 spinning an APC 10.5x4.5. launch at 10300rpms which will give you an idea of its power:
The engine with the stock muffler weighs about 8.1Oz
Some people use the SS30 with a 10x6 prop, much quieter and in a 4.2.4 break mode. But in this setup it is less powerful and will wind up in windy days, not what you want if you compete. For flying in a regular day this is quite fine though.
Martin
Martin