Is it safe to carry F&O overnight positions without hedging?

Short answer, No. 

Long answer, it depends on your risk appetite and conviction in the trade. But there will always be certain situations (like the covid crash) which would give you a huge overnight loss if you happen to be caught on the wrong side! Such black swan events may end up eating your years' of profits or even wipe you out of the market.

Always stay hedged and know your risk!

(One exception : You can go for unhedged stock option positions if you are willing to settle the contract with cash if it expires ITM, i.e if you want to take delivery or give delivery of the underlying asset at a certain price level)

Well, it depends on a few factors such as:

• The trader's risk tolerance level
• Quantum of capital in trading account
• The lot size of the F&O contract
• Volatility of the security
• Key overnight events that could affect the price of the security etc.

Before deciding to carry a naked F&O position overnight, always ask yourself one question: If on the next session, the security opens sharply against the direction my position, will I be able to tolerate the losses such that there is not much of an impact on my trading capital? If the answer to this question is No, then it is better to hedge the position (partially or fully). On the other hand, if the answer to this question is Yes, then you may consider carrying an F&O position overnight.

Again, before carrying a naked F&O position, be fully aware of the risks you are being exposed to. Always focus on the risk first. As the saying goes, manage risk, reward will take care of itself.