Tray Surfer, we do train our ISPs, keep them current on all the Emergency stuff, firefighting, etc... In addition to the operator's requirement they do hangar-based training on the doors and emergency exits, and additional medical training with regards to our pax's needs..
However when there is an enlarged flight requires 3 pilots, the ISP loses on all fronts: less storage space for the catering, only the cockpit jump seat to have a sit-down, and she does the whole flight without hour limitations. I