Looking for a US Broker with Flexible Margin Rules for Box Spreads on SPX/NDX

I trade box spreads on SPX and NDX, but most brokers impose limits based on the ratio of net liquidation value to short options value or total securities value. This restriction makes it difficult to maximize leverage on high-dollar securities like SPX and NDX.

Interactive Brokers and Schwab allow up to around 30:1, but does anyone know of a broker that doesn’t enforce these ratios as long as the account remains in good standing and above maintenance margin requirements?