MRVL stock | How to short MRVL stock | What if I know that mrvl next 5 days goes down 40%, how to short using option,not maximize profit,just balance risk and reward

 Continuing the same Nov 2 worked example ($191 start) — as a design exercise, not a trade for this week. At today's ~$153 price all these strikes re-derive; don't transpose the numbers.

**First, the coach line:** in a real plan "I know" gets replaced by a trigger. For the math, we assume your scenario: **−40% in 5 trading days → $191 × 0.60 ≈ $114.60.**

**The balanced structure: a bear put spread** (buy one put, sell one put below it, same expiry)

A single long put is *not* balanced for a 5-day call: the premium is expensive, theta eats it daily, and if the drop follows a news event, implied volatility crushes afterward — you can be right on direction and still lose. The spread fixes all three: the sold put pays back part of your premium, and theta and IV crush hit both legs, mostly cancelling.

**Strike choice — this is where balance is decided**
- Buy leg: near the money, **$190 put** (delta ≈ −0.50)
- Sell leg: **not** at your $114.60 target. A $190/$115 spread is $75 wide — expensive, and it only pays fully at expiry. Balanced choice: sell the put about halfway to target, around **$150** (−20% zone)
- Net delta at entry ≈ −0.30, so it starts as roughly a 30-share short and grows toward the full 100-share equivalent as price falls through the strikes — exposure grows as the move *confirms*, which is principle 4 built into the structure

**The risk/reward rule (use this on any real quote)**
- Width = $190 − $150 = **$40**
- Take the structure only if the debit ≤ width ÷ 3, i.e. ≤ ~$13.30. That guarantees your playbook's 2R minimum before you enter.
- Illustrative, at a $12 debit ($1,200 per spread — example number, not a Nov 2 quote): max loss **$1,200**, max gain ($40 − $12) × 100 = **$2,800**, R/R ≈ **2.3 : 1**, breakeven $190 − $12 = **$178** — you only need −6.8% by expiry to break even, not the full −40%
- If the real debit is above width ÷ 3, the structure fails your 2R rule. Skip it — that's the decision rule, no judgment call needed at the screen.

**Expiry: never the Friday of your 5-day window.** Theta is fastest in the final days, and a move arriving on day 5 leaves you racing the clock. Balanced choice is the *following* Friday — roughly double your horizon. Slightly more premium, much slower decay, and a buffer if the move comes a day or two late.

**Size, as a formula:** spreads = your fixed $ risk per trade ÷ (debit × 100). If one spread's debit already exceeds your risk cap, narrow the width — never just take it anyway.

**Written exits, before entry:**
- Profit: sell to close at 70–80% of max value. Don't hold for the last dollars into expiry.
- Time stop: a 5-day thesis is half dead by day 3. If the move hasn't started by then, timing was wrong — close it.
- Invalidation: the price level you name that kills the setup.

Three choices lock this module for your journal: sell leg at target or halfway (my math above argues halfway), the debit ≤ width ÷ 3 rule, and the double-horizon expiry rule. State them in your words and I'll record them as your draft short module — collected, not enabled, until you say so.