Flying are easier to do in stages. When someone brings in multiple birds to go "together" I try to talk them into using seperate pieces of wood instead of a single one. The reasons behind this are you can use them together or if you ever change your mind and want to seperate them....you can. If you want to add to the "flock" look down the road....you can. Now if someone is adding to an existing mount I always insist on an actual picture of that bird so I see what I am working with. You don't want a flock of identical poses or a cupped one along side a taking off. People tend to describe something totally different that what I was thinking so I take all the guess work out of it.
With it being so close to season, I would keep what you already had and wait until the end of the upcoming season to see if your other pieces to the puzzle are collected or not. If you decide to just wait them out, take about 6 paper towels and SOAK them. Wrap them around your bird to make sure everything is covered (especially the head and feet) so when it freezes you have created an ICE caccoon around it. If done correctly that bird will last for YEARS without concerns of freezerburn.