I don't know if you saw my post on your other thread, but it's natural for them to fuss until they establish a pack order. Even after they become buddies, just like people they may still bicker once in a while.
Just keep a close eye on them until you feel comfortable. Especially the little one!
My little Dublin (7mos) sits and barks at the older dogs, and he's learned that they may snap or growl at him but they never hurt him (all my dogs are very sweet natured) so now it's become a game to him...
