The last few vehicles constructed were used as test-beds for features in the upcoming Hitachi train design. 560BT, when issued to service, had a short stainless steel exterior panel between the centre windows. [http://vicsig.net/photo/1137] Similar stainless steel panels were placed around bridgeworks at East Richmond, the purpose of both to check for weathering and cleaning methods. The last six trailer vehicles, 891-896T, were 75 ft long over body instead of 60 ft to test clearances at platforms and junctions along with passenger flows. However, the cars were significantly heavier and when coupled to 700-series motors already featuring weaker acceleration further impacting timekeeping.