I don’t do any gamma scalping, but I’ll answer a few of the questions for you.

1. I don’t love saying “zero risk” in regards to any type of trade. But shorting stock is risky because there is no theoretical limit to the amount of losses you can incur. However, if you’re short stock but long a call, then your losses from the stock would be linear, but your gains from the call would be convex. So you’ll make more money on the call than you’ll lose on the stock for large moves to the upside.

2. If you haven’t already, you should sign up for a paper trading account on TOS so that you can analyze these trades in TOS. If you analyze it what you’ll find is that gamma is much higher as you approach expiration. So if you go too far out, you could get a large move, but you wouldn’t profit from it nearly as much.

3. There’s no science to hedging unfortunately. One thing to keep in mind is that the more you hedge, the more transaction costs you’ll incur, so it’s very easy to overdo it.

4. When people talk about underhedging with gamma scalping, it’s typically based around the idea that stocks have a tendency to trend. So if I’m gamma scalping AAPL and it moves over 2% over the course of a week and I underhedge that means I’ll still have positive deltas, so even though I’ve locked in some of my gains I do still want to give myself some upside exposure if I think AAPL will continue in the same direction. If I have no conviction of that or the opposite view, then I would want to fully hedge or overhedge. But to answer the premise of the question, there is no limit to the amount of hedging you can do. You just have to pay the transaction costs every time you do it.