Thanks for asking. When I was doing the mod I kept thinking that I should do this kind of post in case someone else wanted to try it. You motivated me to actually do it. So...
How I Extended the Handle of a Logitech G940 Joystick. I tried to make the mod reversible so there is no cutting or soldering involved. It has been about 2 years since I did this mod so I am a little fuzzy on some of the details. If something doesn't work as described that is why.
Photo 1 - The handle with the 5 screws removed, the bottom hooks released and the right half removed. The red arrow points to where the top of the 1/2" i.d. copper pipe goes in the handle. The bottom of the pipe will rest on the top of the shaft and the top couple of inches of the tube will take the place of the shaft inside the handle. The green arrow points to the connector that will have a "jumper cable" added to the plug. These are only wires that run through the handle into the body of the joystick, so they are the only wires that need to be extended.
Photo 2 - A better view of the socket and plug with the little circuit boards moved out of the way.
Photo 3 - The plug with the original wires. I think that I had to lift a tab to pull out each of the wires.
Photo 4 - One of the 2 pairs of wires that I found to make my jumper cable. These connectors slipped out of their socket after prying up the tabs. I stuck one of these on the ends of each of the original wires and wrapped the connections with electrical tape then the other end went back into the corresponding hole in the white plug. There should be lots of alternate ways to extend the wires.
Photo 5 - The extension in place. The plastic tape wrapped around the end of the pipe is indented with the impression of the other half of the handle. That compression of the tape holds tightly enough that I didn't have to try to reproduce the tabs found on the original shaft.
Photo 6 - This is the clamp that I made to attach the extension pipe to the shaft of the joystick. It is an old piece of 1 X 2 that I cut in half, screwed the pieces together and drilled a hole down the center of the joint that is the same diameter as the shaft and pipe.
Photo 7 - This is the inside face of the clamp. I used a chisel and utility knife to cut the notches for the tabs on the shaft into both halves. The tape gives the pipe enough friction to keep it from sliding or twisting in the clamp, but I can twist it a little to line up the handle with the base.
Photo 8 - The whole thing assembled, mounted on a kitty litter bucket that is cut down to bring the handle to the most comfortable height for me and bungeed to the side of my chair for stability. It is not pretty, but it works quite well. The extension made an immediate improvement in my shooting. I feel like I have much finer control with it. It started as an 8" extension then increased to 12" just by changing the pipe. Fortunately, I started out with extra long wire just in case. I keep the Force Feedback on full. I can definitely feel it but it doesn't seem to throw off my aim like I thought it did before the mod.