So my friend that is now aggressively pursuing homebrewing borrowed by immersion wort chiller to brew a AG 5 gallon IPA. While chilling the wort, he stepped away for a short while and came back to find the chiller was leaking water into the wort from the intake point (clamp wasn't tight enough. I feel that bad that I didn't think to warn him to check it since we've had some huge temperature fluxes recently).
So he pulled the hops out and attempted to boil it down over a couple of hours. But, alas, he still ended up with near 6 gallons at 1.044. Original goal was 5 gallons at 1.065 or so. At this point, I think he'll just have to live with it.
But I thought I'd open the situation up to any ideas as to how to best try to correct an "over watering" situation such as this just in case a similar situation happens in the future *knock on wood*.