Length of self-trim for T-shirt neckline
When working with knit fabrics, e.g. T-shirting with a 25% stretch: I would like to know if there may be some sort of formulae which one could use when finishing round and V-shaped necklines with a self-trim. In the olden days we worked with 3/4 : 1 [e.g. 33.75 cm binding : 40 cm length of neckline seam], but this formulae does not seem to work any more, neck edge seems puckered.