I remember buying jumbo note cards after my professor said we were allowed to bring a notecard without specifying the size.

I also remember commandeering my school’s ultra high resolution poster printer in order to print notes in extremely small font, alongside using LaTeX to let me format the document in a way that maximized my ability to stuff it full of information. The person who helped me do that let me know that the note sheet alone cost the school roughly $4.00/double sided page, or 1/100th the lab fee for the class I printed it for, even though that class had no lab and was in a regular, non-lab lecture hall.

In practice simply asking the professor if using a Möbius strip is acceptable will get them to amend the rules to allow double sided.

Möööbius sheet

it’s Möbius stripin’ time