I just made several of the little size. I think longer pieces might be a problem with breaking. I wrapped the metal tape in duct tape, only used the tape way at the end of the measure,where it did not get used as much. I did not cut the tape as long as the pattern stated.
I left 3/8" to 1/2" on each end of the casing. did you use interfacing on the casing ? PM is you have any other questions.
I love making & giving these little purses ! smitty