RE: Raising stall speed?
Well if you want the wing to stall at a higher speed add stall strips to the leading edge, basically these are triangle stock on the leading edge of the wing to promote seperation. They use them on full size aircraft to taylor stall characteristics, and are generally found at the root of the wing.
I don't think ya really want this. Generally trainer are designed to have a slow stall speed. What you really want is the aircraft to slow down faster for better flight path control. Fixed spoilers or a different pitch prop would do this. A fixed speedbrake (maybe a piece of tape between the landing gear) might also help to give it some more drag for a steeper approach. This might be something to try. Of course I would add a little tape at a time and see if it helps.
Steve