How do I set up a default permission mask so that Windows applications writing to the Mac shared directory can then be edited by other users? Ideally 750. Can a default group be defined for these writes also?

I have tried to find default umask definitions. Running bash by default when using Terminal. If I find or create the umask definition I'm guessing it may fix my Windows writes but maybe cause some other undesired permission problems.

Gory details of my situation:
(names have been changed to protect the guilty)
Both users 'husband' and 'wife' are in a group by themselves called 'husbandwifegroup'. Not sure that matters at this point unless I can change new file group to be named this group name.

Mac Mini Lion Server - share set up for family photos
Mac Air Lion
Windows 7 - wife's system used to get at photos

The share/directory I created ('pictures') and can be seen on Air and Win 7 systems. I also made a group called 'husbandwifegroup' trying to limit other users on the Mac Mini having access.

drwxrwx--- 4 husband husbandwifegroup 136 Nov 27 09:07 pictures

Using this share I can successfully write from Air & Win7 to the shared directory ('pictures') on Mini. But the default permissions are different on the Mini from the two systems when I write files to the share.

-rw-r--r--@ 1 husband staff 35143 Nov 27 12:07 file_saved_from_Air.JPG

Win 7
-rw------- 1 husband staff 12659 Nov 27 12:09 Test husband on PC.docx

From Win 7 logged in as my wife's account
-rw------- 1 wife staff 12622 Nov 27 12:05 Test.docx

So the entire idea for the share was to allow my wife to edit photos from the Win 7 box. That works but when she saves the file it's defaulting to 600.

-rw------- 1 wife staff 3291923 Nov 27 11:16 ./1-1-1.JPG

Same with me on the Air along with the '@' on the end. What does that mean?
-rw-------@ 1 husband staff 195170 Nov 27 11:22 ./1-2.JPG (from the AIR)