Paul,

Tubulators are actually devices that create vorticies on the wing that keep the boundry layer attatched. This helps to improve the efficiency of the wing, especially at low speeds (high AOA). Some full sized planes even have them on the prop!
The correct term for what we're talking about is a cuff, or slat. Generally speaking we're sticking something on the leading edge of the wing to increase the chord at the tip. This is to (hopefully) keep the tip flying when the root stalls. We can do this by decreasing the angle of attack on the tip (washout), or increasing the tip chord. Additionally, the large scale guys figured out that a blunt leading edge stalls "softer" than a sharp leading edge. For your airplane you could take a 12" piece of 1/2" square stock and just tape it on the leading edge at the tip. It works, but I don't use them, I'll usually try to get rid of weight first.
Not all Caps need the up thrust, the 1/4 scale just happens to. You'll know if yours does if the CG is within the normal range but the plane climbs while inverted or pitches up with the power off.
From what I've heard the Kange Cap is a great flying plane, I wouldn't expect any problems, just keep it light. Don't put a heavy engine, big fuel tank, dual servo's or lead on it. Just fly it, leave the leading edge cuffs for another time when you're bored.

Chris