Transmission on FreeNAS umask / owner of files

Transmission on FreeNAS umask / owner of files

going slightly crazy with Transmission installed on FreeNas 8.3.1 (not in
a jail)
Everything is fine except the ownership / permissions of the downloaded
files, they are all owned by root and have mask: rwxr-sr-x
I have tried changing 'umask' in settings.json from 0 to 18 (read it
somewhere) but that doesn't help; what I want is for ANY user to be able
to delete these files (rw.rw.rw.), or at a minimum the group, not just the
owner; I don't know what I should change umask to for this to work.
Probably really easy if you understand umask...
alternatively, how do I change the settings so the owner is another user,
not root; i start the transmission on startup as a service /daemon, so not
sure how to do all that.
any tips greatly appreciated!