Been ther done that snowy I used plenty of micro set to make sure that the decal was well and truly stuck you should be able to"feel" where the ejection ports are, I burnished them with a cotton bud to give an outline of the ports ,mine looked slightly concave then used a scalpel to slooooooooooooowly cut them out, just don't have a try after a heavy night out!
Hope this is of help
Nick