SPX has wider spreads (per trade but smaller per $value), smaller commissions, less slippage, longer hours, more opportunities, and better taxation. I’d have to trade 1000 SPY option combos and possibly receive -$0.01 credit each which would be expensive after commissions, while on SPX I can trade 100 equivalent combos and take -$0.10 credit each, which leaves me with $0.05 or better credit after commissions - that’s theoretical profit if nothing happens, while it can swing up and down during large market swings. And not many people buy or sell 1000 options on SPY, while there may be hedge funds that buy 100 SPX options in an instant. They don’t trade SPY options for the same reasons.
I went long at around 8710 on February the 28th but my position size is a drop in the bucket compared to yours. I plan to hold for quite awhile. Let's see how the cookie crumbles. What's your reasoning behind your position? It's fine if you don't want to share it but I thought I'd ask since for some reason no one else has. If I were in your position I would cash out now. @RedDuke the CME's maintenance margins for their BTC futures contracts are around 14,000-15,000 I believe