MrBass The extensions you are talking about are more properly called leading edge cuffs and this is what they are referred to with full scale aircraft and yes the are used on many types. The purpose of the cuffs is to change stall characteristics of the wing in the region of the cuffs. The idea is to delay the stall departure of the airflow in the area of the cuff and the ailerons, this to retain some aileron control at the onset of the stall. The cuffs do this by rounding off leading edge of the wing to a less sharp curve in this area of the wing for a less abrupt stall departure and allowing some aileron control deeper into the stall.

So the bottom line is it is an attempt to have the root end of the wing stall before the wingtip end. Cuffs are just one of many techniques that has been used in all sorts of aircraft including models. Some other examples of tricks to accomplish the same thing are: Wingtip washout, upward reflexed ailerons, progressive airfoil change to the tip (more benign at the tip) Fixed or retractable wingtip slots and leading edge root stall strips or trips (these attempt to trip a stall at the roots before the tips).


All the above is just to keep the wingtips and ailerons flying a little deeper into the stall for control.



That is the theory but as far do the cuff are a benefit to you or not, only you can tell and I,am not about to get into suggesting ya or na. But heck experimentation is half the fun so enjoy.