Back up.

Are "services", such as maid service or meal provided to the tenants?  If not, the rental belongs on Schedule E.  Short term does not change it to Schedule C unless "services" are provided.

Schedule C is only used for a rental if "services" are provided to the tenants (and in those cases, the expenses go directly on Schedule C, not Form 8829).

In answer to your question, the usual method would be 80/83, unless you elect to use the Tax Court method for interest and taxes.