Stone Tunnel OO

Remixed the large Tunnel by InvertLogic. Closed all holes using meshmixer, flattened the back of the model so it can be laid flat on its back for printing (without artifacts caused by indentations) and flattened the 'feet' of the tunnel so it can be placed flat against a flat baseboard.

Resized to %150 of the original model, this should fit a single OO guage train easily. The entrance is now 87mm wide and 70mm high.