Correct. I don't like the negative gamma. Wouldn't vega be in my favor? Theta too, but many of my trades are over within an hour or two, so I don't worry too much about theta even when I'm long.
I've never sold naked options and never will. Markets don't crash upwards, but they sure as heck can go down really fast. If you get an event during your one hour hold, it would do serious damage to your account. Rewards are just not worth the risk.
Well, one could buy a DOTM put to hedge, but now we're right back at a credit spread and its issues. (I don't know if a credit spread structured in this manner would have the problem of not gaining value as the underlying moves until close to expiry. Something tells me it wouldn't, as the DOTM put can't hardly lose any value.)
Haven't modelled Put Credit Spreads but I reckon you'd still get hurt in a sharp fall because of rising IV. Run a few scenarios and see what you get.