The obligation of a guarantor must be neither larger in amount nor in other respects more burdensome than that of the principal, and if in its terms it exceeds it, it is reducible in proportion to the principal obligation.
Obligation Of Guarantor Not To Exceed That Of Principal
Mont. Code Ann. § 28-11-201, under Guaranty -- Liability and Exoneration of Guarantor.
Mont. Code Ann. § 28-11-201