High!
I don't know whether it's the same with the 1680, but on my 880 you can set up the sensitivity of the led. You should be able to set it up as -6dB, -3dB or 0dB. I set it to -3dB, as I really retrack, if I notice a single blinking (esp. with drums). If you had set it to -6dB you might be able to use such tracks, if you have set it to 0dB probably not. Just listen to the tracks VERY carefully... the problem is that I sometimes did not manage to hear it in the rehearsal room and then had to fix it afterwards, which wa kind of an ugly job...
Laura Tyson seem to have commented that the best thing should be between -4db and -12 on the VS-metering. A lot of guys agree to that. If I record rather undynamic stuff of through a compressor/limiter, I like it a little hotter. But caution: it seems you can overload the mix bus when using rather hot tracks. Then you have to drop all tracks, and you might as well have recorded a little lower...
Ciao
Axel