it will vary depending on the temperature of the solvent, i expect it will be a curve, but neither i nor anybee i know has sat down and graphed it out.
There is a project for you!
If you are wondering how much solvent to use for an extraction, err on the side of too much solvent.
btw- MDMA.HCl is somewhat soluble in DCM, so it makes a poor solvent for gassing that freebase in.