I consider myself marginally behind Len as having the most experience of the LP53 but probably number one in regard tuning it.
It was my research and meddling that resulted in John Milewski article in Airgun World, which annoyingly (for me) detailed his engineers work on improving a 53s power. I gave him all the numbers and his engineer producing a very bad copy of my work. Errors were made in his work but it had some semblance of what I had developed, producing 455 FPS. The article was poor, avoiding any accuracy testing, or pellet testing.
His kit was far too tight, following air rifle trends of the time, in the tightness of the guide and the kits spring was poorly wound. The tightness of the guides did not fully release the springs energy and did not release the torque. The advice for the TP reduction was omitted and a wonderful opportunity missed which completely transforms the gun.
The LP53 is moderately rare...I had 2 examples but chose to turn the gun into what I wanted, a better looking, shorter K version, following the lines of 50s match .22 pistols and caring less what the collector purists think of me doing so. I found the guns and paid for them. I am not a collector, i just liked the look and how they handled.
Chucking out the duel spring set, replacing with a HW30 spring, and guiding it correctly releases all the torque. My pod literally spins on the original guide, resulting in no felt torque if it is done correctly. Reducing the TP dia from 4mm to 3mm reduces the slam and peaks the velocity. A special seal i later developed (pics to follow) give a cushion to the shot cycle, making it virtually recoiless with the right pellet. If it had been done right, the article should have shown the gun producing in excess of 500 fps with virtually no felt recoil and zero torque, but the kit was crud and the article not much better.
The groups i have supplied on here are only average of what you might manage but I have produced occasional groups cutting these in half.