About this detail of the Tiger
Dragon's kit includes both the small and large versions of the Tiger's idler wheel. The instructions offer you a choice between them.
But the small idler wheel was introduced about a month before the thicker turret roof [1] . Therefore it's very unlikely that a large idler would be present on any vehicle represented by this kit. You should discard parts B2 and B3.
[1] DW to Tiger 1