So just switch to a strong password that's just numbers?
I've never understood why people go for a simple "PIN" unlock when it's just easy to have a strong password that's just numbers.
You still get a number pad; but there's no restriction on length. It's just as easy to use as the PIN unlock.
It can still be 4 characters if you want (but the 17hour brute force means you should reconsider that).