This is what you start with - a normal Slow Stick wing. 

 

You will want to cut along the last rib of the wing using a Zona saw or an X-Acto saw. Make the cut as straight and smooth as possible. Use a sanding block to straighten the edges if needed. 

 

For this mod you will need some blucor - I cut mine 11" X 12". The 12" matches the chord of the wing fairly well and the other measurement can be whatever you might need or want it to be within reason. I wanted a total wing span of 60". Score the blucor 3" from the LEADING edge and then bend it over a countertop or whatever you have to get it to match the undercamber of the SS wing. 

 

Here you see a side view of the scored and shaped wing addition. You can do this to the joiner peice as well for a better fit. What you want here is to as closely as possible to match the curve of the undercambered SS wing so that a good butt joint can be made. Then I placed my wing on some wax paper and layed down a thin row of hot glue along the outer edge of the wing and quickly slid the new section into place matching the edges together. A few seconds later and you have a much longer wing!! 

 

Here is the wing after the hot glue joint has cooled and the wax paper has been peeled off. No sanding necessary!! 

 

A 3" wide support joiner is added - again using hot glue. I use a hot hot glue gun - not the low temp one. The joiner just centers up over your butt joint and adds strength at the joined area. Should you feel the need you can add connectors here later for struts. 

 

Finished product - mine actually is 60" in span. It works like a champ on my AP Slow Stick which with the Canon s200 has an AUW of 42 oz. and flies VERY WELL!!