i have to agree with rowuk on this one. Constantly switching mouthpieces doesnt give your muscles enough time to learn what they should properly, and could very well impact the player farther down the road. as for the OP, i went through an embouchure change very similar to you a couple years ago and had the same problem. as Rowuk said, log tones and relaxation are the key. i find lip bending and free buzzing to be really helpful with this. try the lip bending exercises in the schlossberg book, thats what helped me the most.