Recently, I found that if I sell short SHV (short US treasury securities, non-volatile price), I only get charged 0.5% per year. It is about twice cheaper than borrowing money from a broker and keeping a negative cash balance on the account. Is it a good idea to borrow money in such a way and buy investment-grade corporate bonds that mature in 2-3 years? Currently, those bonds yield about 1.7% per annum. What are the risks? How much will the 0.5% fee change in the event of a panic?