20mgs should be enoughabye even less and yes you can get mentally addicted to it after one use cause you usually fall in love with the high then never forget about it but physical dependacy only comes after about a 3-7 day binge of daily use for the most part. Just wanted careful I know I won't be able to talk you out of doing it but I was just like you at one point then tried it and haven't stopped chasing it even ten years later its ruined my life and changed me for the worse. I'm in my early 20s yet I feel like an old man my livers shot,my kidneys are damaged, all my medical problems are exacerbated beyond belief ,I've screwed up every relationship I've had and lost my zest for life most of all. I wish I never do it the one time but I did I chose this life now I got to play these cards. I'm lonely and miserable thanks to oxy it lead me to IV heroin and I will forever be an addict.
Once an addict always an addict remember that.