bigO, your enthusiasm makes me laugh dude! I couldn't find a newb with a better first-time response than yours, to demonstrate why I suggested this design. I don't know who Charles Pirkey is. I don't know whether his design was pure dumb luck. I do know that one would be hard put to find a more ideal first trainer: Not considering the RC components, it only costs three or four dollars and a few hours to build. It's stable, forgiving, durable, and has a wide performance range, including just about every aerobatic maneuver possible with a rudder/elevator model. That cartoon-like tall fuselage (which actually looks very convincing in flight) with its exaggerated pendulum effect, and the wing with its slightly curved high-lift airfoil make this airplane a very stable floater that almost flies itself, and yet you can wake it to perform some very sprightly aerial dances if you like. I suspect that some of those factory-made trainer types are so dumbed down, that by the time you can take-off and land it, you're bored.You seem to have reached that point after one or two flights with the STC! You're ready for an aileron trainer already! I beseech you though, to keep flying it for awhile and try to feel its nuances a bit more. Have you tried spins, barrel rolls, loops, crosswind landings, its handling characteristics in various wind velocities? How strong a wind can you fly in before you lose control - and when you do, can you you get it back? Did you find a slope-like situation and try to thermal it? Even after you advance, I bet you'll find the STC to be a great model to keep in your trunk for a quick, relaxing 10 minutes in the park on the way home.
I understand your enthusiasm for wanting to convert to low wing, but the STC does have its limitations. A biggie would be those struts. This wing design is very effective, but it would not have the required rigidity without the struts. And without the stabilizing factor of that tall fuselage hanging under the wing, you would need to substitute a bunch of dihedral (or ailerons). Look at the thread where I show the model I came up with after the STC (and where I get accused of not being beginner enough). Although I used the same general control surface areas as the STC, the exact same power and RC components, and even the same wing - just an inch or two wider than the original, it really is a completely different design, and flies nothing like the original. But I wouldn't be as able to distinguish the subtle differences had I not put in several hours with the STC.
At any rate, congrats on your successful build and your successful first flights. Obviously, you feel as I did when I first flew it as a beginner. You're on your way son.