First of all, isn't it true that nonpolar solvents like naphtha tend to break down cell structures? If so, were one to perform a straight-base extraction from powdered MH, wouldn't it be preferable to soak the powder in npt prior to the actual extraction? Even if this is not the case, past experience with DXM extraction has taught me that the best method for such an extraction in the case of cough syrup is to premix the npt and syrup to immediately maximize the potential for contact with the freebase molecules. Not to mention that this would decrease the need for shaking and stirring, perhaps?