well i have tried the 100- 115 mg range and (i dont know the exact dosage) , it was swallowed though immediate release (not xr) , well i felt the most euphoric ever feeling but it was followed by intense paranoia that lasted for hours, i felt terror for hours, it was a horrible experience.
id consider this (btw these could easily change based on the route of administration , other substances, personality, weight,etc.)
light: 25mg -40mg immediate release
medium: 40-100mg
heavy:100mg -160mg (btw heavy doses can induce temporary amphetamine psychosis (paranoia, mild hallucinations, etc.)
very heavy:160 mg plus (ive never tried this dose, but its likely to cause amp psychosis , espescially if done long term