Same Group UUID On Two Systems?

Question

I sync files between an iMac and a MacBook both running 10.5.4. The source files are accessible by group "abc" on the iMac. The same group "abc" is defined on the MacBook. When these files are copied to the MacBook the group "abc" is shown as "Unknown".
It looks like the reason the "abc" group is not recognized on the MacBook is because the group UUIDs on the iMac and the MacBook are different. Both groups have the same GID.
So my questions are:
1) Are the different UUIDs the reason for the "Unknown" group name on the MacBook after I copy the files from the iMac?
2) Can I fix this problem by changing the group UUID on one of the systems so that it matches the group UUID on the other system?
3) Are there any ramifications of making the group UUIDs match on two different systems?
Thanks.

Answer 1

The two machines are connected using ethernet/airport and TCP/IP.
I defined the group "riegners" for the first time on Leopard; it is not a carry-over from Tiger.
Here is an example file on the iMac. Notice that the group is not 507, which is "riegners" GID. I used the Finder to add the group "riegners" to the file, which looks to be implemented as an ACL.
Riegner-iMac2:Birthdays dick$ ls -lade xyz
-rw-rw-rw-@ 1 dick _dick 568607 Jul 6 15:34 xyz
0: group:riegners allow read,write,append,readattr,writeattr,readextattr,writeextattr,readsecurity
Riegner-iMac2:Birthdays dick$ ls -laden xyz
-rw-rw-rw-@ 1 503 503 568607 Jul 6 15:34 xyz
0: AEABAE65-4DA4-47CD-99F4-CAF9D4CCDF61 allow read,write,append,readattr,writeattr,readextattr,writeextattr,readsecurity
And here is the same file as it appears on the MacBook after the copy:
Riegner-MacBook1:Birthdays dick$ ls -lade xyz
-rw-rw-rw-@ 1 admin1 wheel 568607 Jul 6 15:34 xyz
0: AEABAE65-4DA4-47CD-99F4-CAF9D4CCDF61 allow read,write,append,readattr,writeattr,readextattr,writeextattr,readsecurity
Riegner-MacBook1:Birthdays dick$ ls -laden xyz
-rw-rw-rw-@ 1 501 0 568607 Jul 6 15:34 xyz
0: AEABAE65-4DA4-47CD-99F4-CAF9D4CCDF61 allow read,write,append,readattr,writeattr,readextattr,writeextattr,readsecurity
Notice that the "riegners" group UUID is the same on the copied file on the MacBook. But the group "riegners" on the MacBook is defined with a different UUID. The Finder on the MacBook shows a group of "wheel", which is correct. And another group of "(unknown)", which I suspect is the ACL for the group "riegners" from the iMac. The group "riegners" on the iMac has a UUID of AEABAE65-4DA4-47CD-99F4-CAF9D4CCDF61, which is unknown to the MacBook.
So if I make the UUIDs for group "riegners" the same on both system will the Finder display the actual group name instead of "(unknown)"? Is it good practice to make these UUIDs the same?
Thanks.