I've been burned a couple of times lately attempting to do what I think you're doing, viz. shorting below "round number" resistance. I fear the 5000 "zone" will provide many more such money-losing "opportunities". I am rapidly reaching the conclusion that margin funds are best invested in SAB.L or even PUB.L at such nervous times.
I have an old long Dec FTSE open, stop still miles away.
FREE CALL CURRENCY>>buy usd/jpy at 9353 sl 9320 tgt 9394-9430or
sell usd/jpy at 9449 sl 9479 tgt 9389-9349(do the call which hits entry 1st n cancel the other one)