Yes. The short extension requires margin approval at Schwab.
Margin introduces additional risk, including the possibility of margin calls during periods of market stress. This is one of the most significant risks of the strategy.
BKLN offers different leverage ratios (such as 130/30, 150/50, or 200/100). Higher leverage may increase loss-harvesting potential but also increases cost and exposure to margin calls and amplified losses. The appropriate level depends on your goals and tolerance for margin-related risk.
Before investing, make sure you understand how margin works and how it could affect your portfolio in different market environments.