re: Can you sell calls to establish a short position?

You're not going to get assigned shares in a short. You're going to have to buy shares, and then sell them to whomever exercies against you. You will left left holding nothing but your loss.

So in other words, right now as I type, you'd need to buys shares at 214.57, and have them sold at 213.5 if the call you sold was exercised. If not exercised, you could cover the option (buy to close) at over a 50% loss. Or wait.

Edit - And your naked trade is down 79% at open. What you collect .23-.79 for, now needs to be bought back for $1.73. Or if exercised, you'd need to buy 500 shares of SPY @ 214.86, and sell 500 shares at 213.50. You are left holding nothing. No short position.

Calls are named what they are becuase you can either call shares away (if you buy a call), or have shares called away from you (if you sell a call). And if you sell a call, shares are called away from you whether you own shares or not.

You're not going to hold anything. What I'm trying to graphically point out to you is that short SPY might, or might not be a bad trade, but the specific way you are describing going short is absolutely insane.

Otherwise, per your last sentence typed in your post above, you're going to have to explain to me how if this is exercised against you, and you sell the shares, how you will be able to hold anything until through September. Because there is nothing left to hold.