RE: Raising stall speed?
Adding incidence will just require more down trim to get the trim back with no other changes. Not a good idea.
The reflexing of the ailerons may or may not help. I suspect that any change would be minimal or unnoticable.
Adding weight is the best option but it'll affect a lot of other stuff as well. You may have to live with just flying it nose high until it stalls.
Often times the engine is running at a higher idle setting to ensure positive running. But with our typical grossly over powered trainers these days even a slightly high idle may well have enough power to delay the speed reduction and eventual stall. I'd tend to start on that front first.