Originally Posted by
cny-bikeman
...and stretch it for a longer time than a few hours. The pricier tubulars tend to be smoother.
Stretching (if not overdone) does make it easier to mount evenly. However back in the heyday of tubualrs even the best tires such as Clement Compionato del Mondo, (Tipo 13) and Criterium Seta (Tipo 6) could be mounted poorly enough to vary in section by over 1/8".
I still use old fashioned gum mastics that allow mounting into wet glue which make it easier to reposition ans square up a tire so it has uniform tension and no wobbles. With the modern glues that are more like contact cement, you need to develop a feel and get it right the first time.