Well if one follows Clarky's thread and modifies the weight of the piston (adding 18 grams to the head of the spring) and the type of spring itself, velocity comes up fairly easily to the 460's with a 7.5gr pellet. Not a lot of effort to bump pellet speed around 90fps over factory specified velocity.
http://www.airgunbbs.com/showthread....53-and-Lucznik
But for accuracy, well... your mileage may vary. Admittedly I haven't put in a lot of hours with mine yet, though I intend to this summer as it'll be along on camping trips. But so far I'm lucky if I can hole 1.5" groups at 6 metres. I can hold 1/2" at that distance with a Pardini K12, owing to the many hours put in training for formal 10 metre competition. Haven't pursued a two-handed grip on the LP53 either which might be key - I just don't like shooting that way, single handed seems more appropriate for pistol to me.