I used to do bear call spreads when I first traded options and used to work pre-Trump, post-first-rate increase. Unless we get a true confirmation of a bear or neutral market, these things are dangerous in up markets. My personal observation of a slingshot move, can be painful. However, it's definitely something to be explored given yesterday's correction. I do have some call ratio backspreads on SPX, where i might make into bear call spreads if have another down day.
Regarding margin, during high VIX, my margin gets (negatively) impacted even with call spreads. IB hasn't been too forthcoming on how their PM calculations work. Makes it difficult to optimize position sizing.