Here's a bit of math to quantify the difference between 20% and 80% drawdown.

If one is 20% in drawdown, i.e. the account is at 0.8 of the previous peak balance, the account needs to grow 25% ((1/0.8 -1) * 100%) just to recover.

If one is 80% in drawdown, i.e. the account is at 0.2 of the previous peak balance, the account needs to grow 400% ((1/0.2 -1) * 100%) just to recover.

Now, 400% is some SERIOUS growth. But things are even worse than that. If you would like to keep the remaining 20% of capital, and not continue gambling, you would need to adapt risk management to the new circumstances. Because your account is now 5 times smaller than before, you would need to use smaller margin/leverage/position sizes. 5 times smaller. And then profit 400% with such a small leverage.

So, in my book, the account that is 80% in drawdown is already ruined, and it's pretty safe to say that it can't possibly ever recover. Unless you're EXTREMELY lucky, of course. But, if you're so lucky how the f*** have you managed to lose 80%?

To finish the topic, I'd say: model for 10-20% drawdown, then expect 20-40% in the live trading. Don't go over 40% under no circumstances, rather throw in the towel and go back to the drawing board.