Hi, I have a stock Stark VFC Glock 19 and I am wondering about recommended upgrades... It's for training so I am not worried about gas efficiency, I am more interested in accuracy, FPS and reliability. I have done some research and I think I know the most commonly upgraded parts but I wanted to get your opinion as to what you recommend? Based on the diagram are there any parts you A: Wouldn't bother upgrading / B: Would upgrade but with a different part or manufacturer / C: Would upgrade but I haven't listed...? I'll be getting a technician to actually do the work so not worried about difficulty. Thanks!