Posted this response on the other site, but for those who might be facing the same problem, here it is again.
I have a half-dozen sets of Bear TD limbs, from old red tips and white tips to new red and black tips, and no two are the same length. There's as much as 3/8-inch difference in individual limb length from my shortest set of limbs to my longest set of limbs. That translates into 3/4-inch difference in bow length. In short, there is no truly standard string length. Need to find what works and buy or make subsequent strings that length.