No weight spacers with 5020ss or you will start jamming and slow2tapping. For 2 years of testing i've tried almost all combinations of 5020ss, stock, 5006, mbx, taccom magnetic delayed, new russian heavy 350 / 450 and more more other buffers with 7 different springs and spacers and sht with and without inner bolt weights +all PFs from 127 to 138..TLDR They all feel ok. Some better some way s#!tter(some even exploded my rifle lol). The best for me was 5020ss + A5 + Polished Carbine Spring + max spacers + 134PF with bcg weight or 130pf without it . Every humanbeing is a different walking machine so you should try it yourself. As for now i got a complitely different new pcc (V-AR) with all shenanigans i was needed inside (shortest reset possible with the lenght of an ammo cartridge/ delayed system/ tuned with par springs ideal weight buffer/ a shuttle level inside finishing and coating so i'm done with testing and shooting it as it came from a box as i am tired of testing.. Better investment is a 20-30kg weight loss. In video section i posted my last vid there i shoot with my 5020ss(red rifle) and a new one(black) i'm happy with both. the black shoot faster and flatter tho..Red is looking better