You couldn't do FYN2 from the existing tooling as she had an odd boiler, fitted during her time with the LSWR, with Drummond pattern safety valves on the dome. Strangely that was one of the accessories included in the original Dapol tooling, despite the dome being moulded on!
Of the IWCR fleet, I believe 9 was the only one to carry the garter livery, all four had the metallic red. AFAIK the extended bunkers came at the same time as the repaint into black, but only 11 and 12 received A1x boiliers prior to the grouping, 10 being rebuilt after and 9 being scrapped still carrying the A1 boilier.