Just posting my personal experience with the LX installation process.
Using ReTro Valve, black hopper right powerfeed body, agd flatline 68/3000 tank. output pressure at 850~900. Velocity unknown after testing (no chrono) since I want all the leaks and misc. problems solved before putting paint through the marker.
-Used 5 line carrier (3 on front then 2 on rear) 2 shims, longest spring. Problem massive leak down the barrel.
-Used 2.5 carrier, 2 shims, longest spring. Problem massive leak down the barrel again.
-used 2 carrier, 2 shims, longest spring. Problem massive leak down the barrel.
The previous three leaks were due to the carrier being too loose around the bolt.
-used 1.5 carrier, 2 shims, longest spring. Problem gun would shoot then stick. STOPPED LEAKING THOUGH!
-used 1.5 carrier, 2 shims, medium spring. Problem gun wouldn't shoot. Solution turned up velocity to unknown amount (no chrono available oops). new result gun would shoot and bounce back with nothing there at lower velocity setting and as i increased it the gun would resume shooting normally and bounce back if i held my squeege in the chamber (down the barrel, haven't tried down the power feed yet). UPDATE gun shoots fine but developed a small leak after about 50 shots. Proposed solution according to an earlier post on this thread it was said that using the next smaller carrier will stop this leak. I have yet to try it. I will reply once I tried it with my final setup.