The direction is what you need to get correct. If you want to skew the S&P short. You can use SPX or SPY or /ES long puts and/or short calls. Or you could even just do it with SPXU. It don't matter.
Or you can fake-trade synthetics at unpossible prices!1 Dude, I just (seconds ago) bought the SPX synthetic at 4478.03!
Don’t lie about fills. Don’t represent sim as real and don’t lie about the structure or venue. It’s a Cardinal sin. All you’ve accomplished is to show everyone that you’re full of shit and your nick is taint.