Not trying to knock myself out of a sale here, but dacron is dacron. A flemish string will settle in more initially (much less if pre-stretched, but will still settle some), but once shot in that part is done--then it's the stretch/creep factor in the material itself (assuming the string is made properly).
'Course this will vary with the draw weight, number of strands, etc.--but I've never used a dacron string (endless or flemish) that didn't require "tweaking"--especially with a heavier draw weight.
That's one of the reasons I prefer the "high performance" materials--cuts way back on that factor--even with flemish strings.
Chad