@ engkin : Many thanks.
Aaargh, lot of code to change and...
with SetLength(mymultiarray, 1, 1, 1), it set length for each array.
With the fpc 2.7.1 syntax, you can set only the length of last array.
Or maybe does it exist something like : SetLength(mymultiarray, -1, -1, 3) but i do not find it in doc