RenTec does use a lot of leverage, but they only can do it because there Sharpe ratio ((return-riskfree)/volatility) is over 7x. This means that if there fund had a unlevered return of 3.5% then their vol would be 0.5%. Let’s say their risk limit is to cap vol at 10%, this means that their theoretical return would be 70%. It doesn’t exactly work like this because of volatility drag. If you’re interested check out my blog post on the topic: https://smabie.github.io/posts/2019/10/04/vol.html