OK so here is the deal: Every ester goes into solution differently. Depends first on the viscosity of carrier oil (GSO, cottonseed, EO, ethanol, ect.) Second is percentage of Benzyl Benzoate which is a solvent. (typically BA will always stay at 2%)
-- Longer esters can be stable at higher dosage hence why you see deca at 300 and eq at 300 (EQ is almost a liquid in raw). With a combination of different esters and using EO as the carrier, and possibly even more BB to thin it out... You can reach some high mg/ml.
-- Certain AAS like Test P and NPP I personally would never trust above 100mg/ml. Yes, They will hold above 100mg/cc and not crystalize at like 150 or 200 but suppppper painful. (another reason I really don't trust "cut stacks" with 100 tren, 100 prop,and 100 mast.) That blend can be done yes, but it takes some pretty creative measures to create said blend. I will tell you most of the time they are under dosed as to lesson PIP.
Many things are possible I know this, But personally I would stay away from like test 400/500 stuff like that.