pulling to the right

Recently I had my local shop install an MC36221 dual master cylinder (per the recommendation from this site), along with new front drums, shoes and wheel cylinders. The car stops great - until the brakes warm up a bit. Then, I notice there's some pulling to the right, especially on a hard stop. Occasionally, I've heard a screech. I don't seem to be leaking any brake fluid; is it likely I need to back the shoes off on the right a bit, or could there be another explanation?

Thanks
Dan