[LAD] (libsndfile) FLAC format question

Hi I would save a internal audio buffer to file on exit, to reuse it after e new start. Currently I use stdio fopen/fwrite/fread and save the binary data from the array. That works well. Now I've started to play with libsndfile, first I use SF_FORMAT_WAV | SF_FORMAT_FLOAT which work as nice as stdio. The file size is the same then with plain binary data. To save some bytes on the disk I tried SF_FORMAT_FLAC | SF_FORMAT_PCM_24 which reduce the size nearly to the half. The drawback is that the floats in the internal buffer could go out of the range from -1.0 <-> 1.0 which leads to crackles when the buffer get refiled. As long the values are in range, flac works very well. I tried it with the sf_command (sndfile, SFC_SET_NORM_FLOAT, NULL, SF_TRUE) for write and read, but that didn't help. Yes, I use sf_write_float to write/read the flac file, even if flac didn't support floats. When I understand the libsndfile api right, libsndfile will handle that. So my quetion will be, which is the common format to write flac file with libsndfile, and is there a way to write values out of range into a flac file? regards hermann