I am currently scaling a systematic, market-neutral strategy (SPY/SPX delta-neutral rotations) and have hit a ceiling with IBKR’s rigid autoliquidation and lack of portfolio margin flexibility. I am finalizing a relationship with Clear Street and wanted to vet their "plumbing" with anyone currently running institutional flow there.

The Strategy ("The Bill"): High-volume, delta-neutral rotations. Specifically: Shorting deep-ITM calls against long underlying, requiring aggressive spread capture and sub-100ms hedge triggers.

The Term Sheet Asks: I am pushing for a customized facility. I’d appreciate feedback on whether Clear Street (or Dash Prime/WEX) is actually playing ball on the following:

1. Custom Credit & Risk-Based Haircuts

Since Clear Street is self-clearing, how much discretion have you seen regarding intraday leverage for hedged books? I need a risk-based exclusion for my box spreads and a lower margin coefficient on the delta-neutral legs than standard Reg-T or basic PM.

• Has anyone successfully negotiated a "fixed-haircut" model rather than a dynamic risk-based one?

2. Execution: Fox Algos vs. Adverse Selection

My strategy relies on capturing the Midpoint/Ask on option legs before quotes vanish.

• Fox Blaster (Aggressive Arrival): Does this actually "sweep" effectively, or is the signaling risk too high?
• Fox Dark Attack: For IWM/SPX, are you seeing genuine price improvement in dark pools, or is it just adding latency to the fill?
• Manual vs. API: For 25¢ gaps, is their API SOR smart enough to join the COB passively, or am I better off using their high-touch desk for "working" the orders?

3. API Plumbing (Latency & Fill Notifications)

I’m building the auto-hedge logic in-house.

• What is the p99 latency on their WebSocket/FIX fill notifications?
• I need <100ms from execution to notification to trigger the share-hedge. Does their cloud-native stack (Kafka-based) actually deliver this, or is there "micro-burst" congestion during peak volatility?

The Bottom Line: I'm looking for a partner, not just a pipe. If you’ve moved from an Apex shop (Dash) to Clear Street, was the "single-ledger" tech actually worth the migration, or is Dash’s options-specific SOR still the gold standard for spread hunters?