5/8 is fine for delts unless u have alot of bodyfat but for most that size is perfect. You will know when u get or have scar tissue in ur glutes when u pin u will hit hard and tough/rough spots u will feel it when u go through it..... It can cause absorption issues but u have to have a pretty good amount of scar tissue there... Even if u pin ur glutes and u move the site around slightly u'll be fine.... If u can the more u can spread ur pins out alil the better off u are and the less likely hood u are to ever devolpe scar tissue.... You usually have to pin alot in the same spot and for it to not have had enough time to heal and also absorb. I would rotate glutes then delts. Then if u need more spots ur looking at chest,lats are good spot, quads but I would try and stay away from them unless u really need them... U can also use smaller needles like really a 25 guage and 1 inch is perfect and what most use, but u could go to a 26 guage 1 inch. The more time u can kinda rotate and give ur body time to heal and absorb the oil is better.... To build scar tissue u gotta be pinning the same spot alot atleast from my experience.... If u got scar tissue u will feel it when u pin u'll hit hard spots. Just rotate a bit more and use those 5/8 pins for ur delts as long as u don't have slot of bodyfat