@docdoc: you are right I need to unterstand the issue, but for this project I need a quick solution. I will work in parallel on the problem to understand it as far as I can.
fill the struct, see above followed by
#define LOCATION_CAL_LIPO 256
myMem.put(LOCATION_CAL_LIPO, calstruct);
all data in calstruct is OK
read_back
myMem.get(LOCATION_CAL_LIPO, calstruct);
and make a dump and "FF" is on position 255
BTW: no change if I shift the LOCATION_CAL_LIPO to another adress