Here's the second of the double-fit hands from the Camrose:
Every table played this one in 5X making: at this vulnerability par is 5. For my part, I understand 4 by East, but if you're going to bid 5 and double 5, I think you should try 4 first, so you can get to a good slam sometimes. I think South should bid 4 if sufficient, because I did, thinking it very unlikely that 4 would buy the contract and that my side would learn something about spades. I made slightly the wrong decision by removing 4, shrug.
I don't think it possible for East-West to defend 5 undoubled. But bidding 6 would be a reasonable attempt to get a plus score, not too costly if it fails.