Icarus Pacific. I sent Kelp monkey drawings of a home made slip tip and how to make it. What have you done?
LaJolla diver. Yes, the Prodanovich gun is considered obsolete but it served its purpose well. The ideas and theories that he generated live on. But some have fallen by the wayside. The Biller gun might be dissed by some depending on the environment, visibility, range, type of game, and ignorance. However, there are several models of this gun and , with modifications, serve the freediver quite well. I would be willing to discuss these mods but one should understand that customizing is particular to each diver and his prejudices, needs and circumstances. I spent years diving the Coronados, San Clemente and other places. My preference in guns for blue water hunting the Coronados is the Island or Blue Water. My preference for tank diving or freediving the kelp is the Island or Biller 54. As I say, the Biller needs to be set up properly for extended range shooting and is really not suitable for blue water where 20 foot shots are taken on big game. It is best suited for close shots on big game or long shots on open water gamefish like king mackeral (east coast). Its strong suit is pinpoint accuracy and that comes into play when a Spanish or king presents a 2 inch bullseye. (The fish are soft and feisty so the shot must be accurate). The usual setup is with 2 heavy bands and Tahitian shaft or three medium bands and sliptip. Always mount a reel, of course.The mix of game in California, eg, tuna, weighs against a gun like the Biller (or Allen) and in favor of custom or homemade guns or guns like the big Riffe's.
PS: If you are having trouble with the Biller trigger it may have to do with the line release. Occasionally, there is friction between the trigger and the metal tab that drops the line. Polish the parts and do not string the line too tight. I didn't say the gun is perfect. Otherwise, the trigger and sear are well made but they, too should be polished if any friction is felt. Normally, that is not necessary. I would not impose traction loads more than 300 pounds but that is plenty for most purposes and the gun trigger still has a margin of safety.
PPS: If someone will instruct me how to do 'thumbnails' I will forward some pics of Biller mods and/or Riffe mods from time to time. Make it simple and specific. I'm a KISS kind of guy ((keep it simple, stupid)