Johncast; yes it is very frustrating! I firmly believe that the properties of the new resin are different enough that they should have renamed it as a new product rather than retain the 4PU name. If you want to check it out I suggest just buying the small 500g sample kit for your own evaluation.
From some brief browsing none of the other Barnes resin products have properties exactly what I'm after. I've bought the 860g Smooth Cast 305 kit from Back 2 Base-ix and I'll post the results as soon as it arrives.
SSB; Yes, the power usage of having to heat the moulds is definitely a concern. I know it wouldn't be massive amounts of power, but it's still just a lot of playing around. Plus I would not want to leave the heater going while I'm not at home and I don't want to have to hang around for hours while it post cures. Indeed the Smooth cast shouldn't be as sensitive as the Task 8.