During testing of SVRy 250 the CMO left the side tanks in place but empty. He wanted to see how the engine did without the full tanks. If the test had not worked out they would likely have run with both side tanks and tender.
As it turned out, the empty side tanks with tender showed that the articulates would in deed work on the line from S. Baker to Bates so the tanks were cut down and the ballast that Bret mentions put in place.
Only #250 was used in testing like this. When she worked out with the empty tanks, #251 was immediately converted to the same tender configuration.
Martin