sector boundary has to do with sector length not actual file size.
Also it has to do with sample rate and length, and not bit depth. If we were to record at 88.2 KHz, we could split those files on 1/75 second points, and that would sample-rate-convert neatly to SBE-free 44.1Khz. 24 bit, 16 bit, 8 bit, still has the same number of samples per second, the 24bit ones just have more resolution!
Hey, so if I record at 48KHz and split files into even multiples of 640 samples, my 44.1KHz output will be in 588-sample increments? This gives me an idea!!