Let me bring you up to speed on the workflow of conforming clothing and models.  I believe many artist do the same procedure as you described and get unsatifactory results when posing the model.  The actual workflow is pose your model, apply the morphs and then add and conform the clothing.  That should apply a better fit.  The introduction of magnets to the clothing will solve most pokethroughs.  I have not had too many successes with these.  Although many hiding body parts also solves the pokethrough issues, I see in your case, that is not practical.  If similar body zone exist in the clothing as the model, copy and pasting may be your other alternative.