"it's a marginally long enough runway"
I have 3500+ hours/2000+landings in the straight 680. If the 5000ft distance given above is correct, than its not "marginally long enough". (as several people in this thread have already pointed out!) You can plant the C680s into 3500ft COMFORTABLY if you know what you doing even at high weights and regarding to Vref close to touchdown: this airplane slows down really really hard with full flaps and idle power. E.g. If you are at max speed for full flaps (175KIAS) at 2.5 nm and youre putting em down and stay in idle, you crash and burn in FRONT of the runway. She flies much like a KingAir 200 with props in high RPM and full flaps at this stage, if that gives you an idea.
What is a nono at least in the straight 680 is force her down on a higher speed (Vref plus say 5 or 10) AND deploy speed brakes in quick movement without pushing the yoke forward. That CAN get you airborne again. (speedbrakes are manually extended and have a distinct nose up effect). This MIGHT have played a role.
What adverse role does a DA in CAVOK play ?