TLT and Cluster Missiles - Will they allow the token to be held to be spent on the second attack when attacking a ship carrying HSCP?
HSCP just specifies "while attacking" and "while defending". It never says anything like "this attack". As far as I can tell when using "perform this attack twice" weapons those windows run from the Declare Target step until they Remove Destroyed ships step without interruption.
This won't be an issue with the ship carrying HSCP as only primary weapons trigger HSCP, but it will come into play when the ship with HSCP is being attacked.