Seems to me, if the objective is to get cars under roof, it wouldn't be terribly difficult to jack up tracks 2 and 3 to meet the new floor and use blocking to hold them in position. Uncover the doorways long enough to move two cars in under the roof, then seal the building up again and wait for spring to arrive. By my count, we have five cars (3, 8, 302, 320, 103) that need to be sheltered, along with the locomotives. Am I missing something?