GWS Slow Stick MODS
The GWS Slow Stick is possibly the most widely modified plane in history, although it will fly perfectly well completely standard.
Here are some modifications, arranged in the order you should consider them.
Modifications that will make the plane easier to fly, or less likely to break,
Do this before your first flight! Bolt a wing nut, or large servo arm to the motor shaft, in place of the prop. Put it as close to the gear box as possible and cut the shaft off so that only a few millimeters are protruding. Place the prop against the prop saver and hold it on with a rubber band or O-ring. Now the prop can be knocked backwards without breaking (or breaking the gearbox).
The stock wheels will break after a few heavy landings. Replace them with something that looks better.
These tend to splay outwards when you land. Bind (or solder) a piece of wire to the middle of each leg. This stiffens it up while keeping some 'spring' in the legs. Don't put the wire across the very bottom of the legs, or it'll get caught on the grass.
You can move the under-carriage legs to the front of the plane. This reduces the tendency to nose over when landing on grass but it makes high-speed taxing harder. Bind the top of the legs to the stick with thread (or dental floss) and soak in glue.
The slow stick needs 3 degrees of down and right thrust, otherwise the trims change as you change the throttle setting. Carve a bit of softwood into a square stick about 3" long that fits inside the fuselage tube for most of it's length. Try putting the motor mount on this, and you'll see that it's a sloppy fit, tip at as far as it'll go and that's about 3 degrees. Carve the other end of the stick so it's at the same angle and a good fit in the motor. I say 'carve' but it's easier to be accurate if you sand it to shape, after rough carving.
These mods are unnecessary, and in many cases you'd be better off buying a different plane instead - except that modifying the slow stick is easy and fun.
To reduce the Slow Stick's sensitivity to wind without affecting it's lift too much, you can clip the ends of the wings off. With a very sharp blade, carefully cut the wing tips off along the last "rib". This will also make the plane a little more nimble and works especially well when ailerons are added.
Cut ailerons the full length of the wing, and as deep as the moulded ones. The "stock" molded ailerons are normally not large enough to be effective. Use either one or two servos. If you use one servo, be careful that it doesn't get in the way of the elastic bands. The dihederal needs to be removed or reduced. If you make the wings straight you can use a single CF spar all the way across the wing. To reduce the dihedral, either straighten the wing joiners, or get some brass tube the same size and bend it to a smaller angle. With a straight wing you will need to correct the roll angle every second or two, so it's good preparation for an aerobatic plane but not relaxing to fly. With little or no dihedral, rolls are possible, but they aren't pretty and require lots of elevator and rudder at the right times to make them look roughly "axial".
Ailerons won't turn the Slow Stick into a Formosa, but the controls will be much more positive.
A 2000mAh 2 cell lipo will give nice long flights for about the same weight as the stock battery but be sure to mount it so that nothing digs into the lipo! Glue a flat plate to the fuselage stick, use velcro to hold the battery in place against the flat plate and a couple of velcro straps around the battery and fuselage to hold it all together. The standard speed control isn't lipo safe, so either change it, fit a lipo saver, or work out how long you can fly for and set a timer.
The easiest way is with two short lengths of square section balsa (or an old fuselage, cut in half). Attach each to the wing, with a motor on the front. Obviously you don't have to stop at two motors...
Another way is with two fuselages, each with their own motor, and an inverted V-tail. This is popular for Aerial Photography as it leaves the center of the plane free for mounting a camera.