Hey,
Did you ever think about using SS pins instead of shark fins? Those fins would require you to weld them on and by doing so, you would ruin the temper of the shaft causing it to become brittle. I stated making my own shafts out of tempered stainless (not sure if it is 17-4). The blanks here cost me $18 and the barb another $2. If you have access to a drill press, a bench sander, a rotary tool and a bench vice then you're in business. First thing you want to make sure that your blank is as straight as possible. Next go over to your sander with your blank and an old shaft. Mark how wide and how deep the cuts are on the trigger lock up on your new shaft. Grind down the flat end of the trigger first. Then using the edge of the grind stone, make a triangular cut into the opposite side of the shaft. Go slow and don't go too deep. To make the trigger lock up round use the rotary toll with a medium sized round sanding attachment and smooth that bad boy out. You don't want to cut the shaft until you have successfully made the trigger end of the shaft and have made sure that it locks in the trigger mech of your gun. Now figure out how many bands you are going to use. Since the tabs are not as strong as the shark fins, you need to make one tab per band. Mark the shaft where you want the pins. As far as a line attachement, you can either make a U shaped pin or go straight through the shaft. I went the easy route and have been using the hole method. You may want to either put a small scratch or even grind down a small flat area before drillng since the drill bits tend to slip on the smooth round surface of the shaft. Lock the shaft up in the vice and proceed solwly. When drilling the shaft use cobalt drill bits and low speed with steady pressure and liberal amounts of lubricant. A good bit size is 3/32 inch. For your pins, use stainless steel of the same diameter. Grind down a slight taper on the last 1/16th inch of the pin. Make the pin about 1 1/2 inch long and lightly tap it into the hole until the tapered end appears. If you have a tig welder good, if not, find a hard flat metal surface and tap the pin until the tapered pin mushrooms on the bottom of the shaft. Repeat the process on all pins and even the line attachment if you so choose use one. When all the pins are done, grind down the excess with the rotary tool. Next put a slight backward bend to the pins and trim them down so only about a quarter of an inch sticks out above the shaft. Bevel the ends to prolong wishbone life. For the barb, I use the same stainless pin material and repeat the process only this time leaving the mushroomed ends. It sounds complicated but it's so much fun machining your own gear, not to mention satisfying when you have impaled a good fish with your own shaft. Hve fun and good luck.
Brad