In actuality, powerlifters who have lost weight have tended to notice improvements in their deadlifts because their bellies no longer got into the way, and they could assume a better starting position.
If you are concerned with keeping body fat low, and 5% is really, really low, unless you are predispositioned to being that lean anyway, chances are you are going to be in a calorie deficit, and thus making it harder to maintain or even increase strength.
There does seem to be an optimal level of bodyfat for strength and muscle gains, and that's probably between 8-12%. Getting really fat improves your leverage somehow, intramuscularly, which is why you see the strongest humans on the planet around 20% or higher (reference...see the SHW OLs or PLs). Note I am talking about the strongest, period, not the strongest, relative to bodyweight.
You know, I like to run off at the mouth, there's no denying that. That 500# DL comment was one of those moments. But, chances are that if you don't think you can get to a 500# deadlift, you're not going to do so. If this is a concern of yours, my suggestion is to seek out a local group of powerlifters to lift with and to loosen up on the diet a bit to put yourself in a state of positive energy balance.
It all depends...you could state "If you are over 20% bodyfat, then you are a fat bastard with no dietary discipline" and POW! you'd have me on the ropes.