Very nice thread. I have very stupid setup but it works for me... Please don't bash me.. I'm a techie guy..
I have a single pneumatic gun 50 cm and use titanium line retainer exactly like vrohlenko posted in the thread. I also replaced original crappy shaft with 26" Pneumatic Speargun Shaft from spearfishing world. It was expensive, $50 but worth every penny. It's longer but flies super nicely and doesn't bend nor rust. I kitesurf and for the line I use 7 meter long kite extension line cut to 5meter which I had lying unused. They are about 1mm/1.2mm at about 300kg/700lbs rating. Super strong. I also have 1W laser guided tech on the gun and some other stuff lol. Some fish are super scared of that tech and for these I turn it off but some big fishes like bass/striped bass don't care and sometimes it helps when you need to make split second shot at a distance. I also pump the gun to 30psi-33psi
Some sessions I don't miss a shot. I'm also a big believer into keeping your spear tip extremely sharp which makes massive difference and sometimes shot fish from pretty far distance.
We had the same idea, a green laser!
Although I gave up on that idea when I couldn't find an underwater laser on Amazon
Is yours adjustable? Is it designed for water or did you tweak it?