Default file right using ftp upload

I use two accounts A and B (same usergroup).
B manages its files and the files of A

A uploads files in its home, nevertheless (it uses windows explorer ftp) most of the uploaded files and dir are 555

B cannot move & delete them… even if it has all the right on the home of A. To block B, just create un dir 555 and a file in it with 555. B cannot delete/move the file because it has not write acces to the directory, and it can not delete the dir because it is not empty

One solution could be to force all the uploaded files to be 774 for example. Is there any option somewhere ?