I would be leery about sending your piece through the mail, but knowing that you live in a remote locale...
1) Insure the piece both ways in transit.
2) Use post it notes to identify where you would like a specific signature.
3) Have the letter that accompanies it clearly state what you want (Blue or black fine-tipped Sharpie, etc.)
4) Call the promoter and speak to the person in charge of mail order autographs and discuss what you're looking for
These steps will insure a better end result, FWIW.
Good luck, it's a terrific piece!
It's sad to note how many players on this poster are now deceased.