Hmm if the mirror has a large hole in the center, you can have one cut and roll it along the tangent. The major radius can be big and the rolled mirror only be the length of the minor radius.
Ie if you have a 45 meter circumference and 5 m hole, the major radius is 22.5 meters but the minor radius is only 20 meters and it can roll into 20 meters. It will have one discontinuity though that would cause artefacts and might destroy any advantages from the additional size.
Ie if you have a 45 meter circumference and 5 m hole, the major radius is 22.5 meters but the minor radius is only 20 meters and it can roll into 20 meters. It will have one discontinuity though that would cause artefacts and might destroy any advantages from the additional size.