What is the rule on contingently payable legal interest?

3 The rule is stated thus: "It is also a general principle that when payment of full legal interest is subject to a contingency so that the lender's profit is wholly or partially put in hazard, the interest so contingently payable need not be limited to the legal rate, providing the parties are contracting in good faith and without the intent to avoid the statute against usury." (Thomassen v. Carr, supra, 250 Cal.App.2d 341, 346, 58 Cal.Rptr. 297, 301.)