[plug] UMASK explanation sought

[Earnshaw, Mike]

Silly question yet again ...

If I have a directory:

drwxrwxr-x support support .... ....

UserA is a mbr of support. When UserA creates something we get

-rwxr-xr-- UserA UserA .... ....

I would like it to remain "support support"

I read on the UMASK man page that a setting is subtracted from from the
mode. So in my example umask of 022 would be subtracted from 775 to give
753 (rwxr-x-wx), but I don't understand how I can make the "username
group" to remain the same.

Any pointers please!

Mike