Yea the SH-5 is the straight Custom. I use them in the bridge with a PG in the neck. While I know I still have the two Customs covered and one in zebra, and also a zebra PG (neck), I'm not sure I still have the covered PG (neck) and would need to double check on that later tonight. Considering its the neck, you could always just add a cover to the uncovered PG (neck).
Did you pull yours from a guitar? If so, which model? You're sure its a 57+ and not two 57's (my preference, actually)